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tamnd's digital brain — notes, problems, research
41348 notes
We are asked to prove the identity \sum_{j=1}^{t} (-1)^{j+1} \frac{c_j^2}{m_j m_{j+1}} = \frac{1}{m_1} \sum_{j=1}^{t} (-1)^{j+1} b_j (c_j + c_{j+1}) p_{j-1}, where the sequences $(m_j)$ and $(p_j)$ co...
The issue is not with the core idea of sweeping and using endpoint extrema per color.
Equation (28) in Section 3.
Let (x)=x-\lfloor x\rfloor-\tfrac12 be the centered sawtooth function and
Hmm.
Let $\sigma(h,k,c)$ be the sawtooth sum used in the TAOCP context, where the key structure is a sum over a complete residue system modulo $k$ of a shifted sawtooth expression of the form \sigma(h,k,c)...
Let $h h' + k k' = 1$.
Let D(a,b;c)=\sum_{j=0}^{c-1} \left(\!
Hmm.
The problem asks for the maximum possible value of $d$ in the notation of Theorem P, given that $m = 10^{10}$ and the potency of the generator is 10.
From Eq.
**Exercise 3.
The previous implementation fails because it blindly alternates the column in a zigzag without checking **preexisting cacti** in adjacent cells.
Let ${Y_n}$ be a binary sequence generated by the linear recurrence over $\mathbb{F}_2$ Y_n = (a_1 Y_{n-1} + \cdots + a_k Y_{n-k}) \bmod 2, with period $2^e - 1$, and initial state not the all-zero st...
The statement is **false**.
We are asked to determine the asymptotic value of the probability that $k+1$ consecutive bits generated by Y_n = (Y_{n-1} + Y_{n-2}) \bmod 2 contain more 1s than 0s, under the conditions that $k > 2l$...
Let the sequence $(Y_n)$ satisfy the recurrence Y_n = (Y_{n-21} + Y_{n-55}) \bmod 2 over $\mathbb{F}_2$.
Let $b_{n,r,s}(m)$ be defined as in Exercise 28: it counts the number of $n$-tuples $(y_1, \ldots, y_n)$ with $0 \le y_j < m$ that have exactly $r$ equal spacings and $s$ zero spacings.
The exercise explicitly depends on results developed across Exercises 28 and 29, especially the generating functions for $b_{n,r,0}(m)$, and it asks for a fairly deep asymptotic expansion whose deriva...
Let $y_1,\dots,y_n$ be i.
Let $U_1,\ldots,U_n$ be independent uniform $(0,1)$ deviates and let $S_1,\ldots,S_n$ denote their spacings in increasing order, so that $0 \le S_{(1)} \le \cdots \le S_{(n)}, \qquad \sum_{i=1}^n S_{(...
Let the linear congruential sequence be X_{n+1} \equiv aX_n + c \pmod m, \qquad b=a-1, \qquad d=\gcd(m,c),
Let $Y_1,\dots,Y_n$ be a cyclic sequence over $\{0,1,\dots,d-1\}$.
**Exercise 3.
**Exercise 3.
Algorithm P (as defined earlier in Section 3.
Let $(Y_n)$ and $(Y'_n)$ be integer sequences with period lengths $\lambda$ and $\lambda'$, respectively, and values in ${0,1,\ldots,d-1}$.
Let the serial correlation coefficient (23) be C=\frac{N}{D}, where
Let $U_0,\ldots,U_{n-1}$ be independent identically distributed random variables.
**Exercise 3.
Let the means of the sequences be $\bar{u} = \frac{1}{n} \sum_{0 \le k < n} U_k, \qquad \bar{v} = \frac{1}{n} \sum_{0 \le k < n} V_k,$ and define the centered sequences $U_k' = U_k - \bar{u}, \qquad V...
In the maximum-of-$t$ test, the $j$th observation is V_j=\max(U_{tj},U_{tj+1},\ldots,U_{tj+t-1}).
**a)** Let Z_{jt} = \max(U_j, U_{j+1}, \ldots, U_{j+t-1}).
Let $\langle X_i \rangle = X_0, X_1, X_2, \ldots$ be a sequence of distinct numbers.
Pattern (15) is the unimodal pattern x_0 < x_1 < \cdots < x_p > x_{p+1} > \cdots > x_{p+q}, on $p+q+1$ distinct elements.
Let $R$ denote the length of a single segment in the generalized coupon collector's test of exercise 9.
An ascending run is a maximal consecutive subsequence U_i,U_{i+1},\ldots,U_j such that
We are given a square grid of size $n times n$, where each cell represents the annual revenue generated by a table in a restaurant. The restaurant layout is a perfect square, so the grid has exactly four corners: top-left, top-right, bottom-left, and bottom-right.
\pi = (1, 3, 5, 4, 6, 2, 7) since (9) in that section is usually this permutation.
Let $Y_0, Y_1, \dots$ be independent and uniformly distributed integers between $0$ and $d-1$, with $d \ge 2$.
Let $L$ denote the length of one coupon-collector segment produced by Algorithm C.
**Exercise 3.
Let $e = 2.71828\ldots$ and consider its expansion in an integer base $b \ge 2$, giving digits $e = \sum_{k=-1}^{\infty} e_k b^{-k}, \quad e_k \in \{0,1,\dots,b-1\},$ where $e_{-1} = 2$ for the intege...
Let $\langle U_n \rangle = U_0, U_1, U_2, \ldots$ be a sequence of independent uniform random variables on $[0,1)$, and let $0 \le \alpha < \beta \le 1$.
Let ${U_j}$ be a sequence of independent and uniformly distributed random variables on $[0,1)$, and let $p = \beta - \alpha$ denote the probability that $U_j$ lies in the interval $[\alpha, \beta)$.
Let I_j = \begin{cases} 1,& \alpha \le U_j < \beta,\\ 0,& \text{otherwise},\end{cases} and define
The serial test is defined in terms of $n$ observations of pairs that are intended to behave like independent draws from the $d^2$ equally likely categories.
For triples, quadruples, or generally $k$ successive values, the serial test is formed by grouping the sequence $\langle Y_n \rangle$ into disjoint blocks of length $k$.
Let $n$ be a fixed positive integer, and let each of $n$ independent trials result in one of three categories with probabilities $p$, $q$, and $r$, satisfying $p + q + r = 1,\quad p,q,r \ge 0.$ Let $Y...
We are given a sequence of positive integers representing strengths of participants arranged in a line. The task is to choose a single split position such that the array is divided into a left prefix and a right suffix.
Let Y_i=\sum_{j=1}^{n}a_{ij}X_j+\mu_i,\qquad 1\le i\le m, where $X_1,\ldots,X_n$ are independent random variables with
Let $X_1,\ldots,X_n$ be independent observations from a distribution function $F$, and let F_n(x)=\frac1n\#\{j:X_j\le x\}.
Investigate the "improved" KS test suggested in the answer to exercise 6.
Let the empirical distribution function be F_n(x) = \frac{1}{n} \sum_{i=1}^n \mathbf{1}_{\{X_i \le x\}}, and define the Kolmogorov-Smirnov statistics as in formula (13):
The previous solution fails because it assumes, without justification, that the finite-$n$ Kolmogorov–Smirnov distribution admits a power series expansion in $n^{-1/2}$ obtained by Euler–Maclaurin app...
A natural multivariate analogue of the Kolmogorov-Smirnov test is obtained by comparing the empirical distribution function F_n(x_1,\ldots,x_s) = \frac1n \#\{\,j: X_{j1}\le x_1,\ldots,X_{js}\le x_s\,\...
Let $t$ be a fixed real number and, for $0 \le k \le n$, define P_{nk}(x) = \int_{-t}^{t} dx_n \int_{-t}^{t} dx_{n-1} \cdots \int_{-t}^{t} dx_{k+1} \int_0^x dx_k \int_0^{x_k} dx_{k-1} \cdots \int_0^{x...
We are asked to generalize Theorem 1.
Let each observation in the experiment be an outcome in a finite set $\Omega$, and let $P$ be the probability measure assigning probability $p_s$ to category $s$, with independent observations.
Let Y_i=np_i+\sqrt{np_i}\,Z_i , where $Z_i$ is defined by Eq.
We compute the Jacobian of the transformation x_k = r\sin\theta_1\cdots\sin\theta_{k-1}\cos\theta_k \quad (1\le k<n), \qquad x_n = r\sin\theta_1\cdots\sin\theta_{n-1}.
**Solution to Exercise 3.
Let the original KS test be based on $n$ observations $X_1,\ldots,X_n$, with empirical distribution function $F_n(x)$.
Equations (11) and (13) in Section 3.
Let the 20 values of $K_{10}^+$ be X_1,\dots,X_{20}, and let the corresponding 20 values of $K_{10}^-$ be
Let the original chi-square test be based on a partition of outcomes into categories $1,2,\dots,k$.
Let the underlying distribution function be $F(x)$.
In Section 3.
The statistic $K_{10}^{+}$ is computed from blocks of length $10$, but the Kolmogorov-Smirnov test in this exercise is not being applied to the original observations within those blocks.
Let the first die be fair, and let the second die be loaded so that it can show only $1$ or $6$, each with probability $\tfrac12$.
The value $V = 7\frac{1}{16}$ corresponds to the chi-square statistic computed from $k = 11$ categories, as in Eq.
**Corrected Solution for Exercise 3.
Let the first die be biased toward the value $1$, and let the second die be biased toward the value $6$.
**Solution to Exercise 3.
Let f(x)=a x^{-1}+c \pmod{2^e}, with
Let f(x)=x^2-cx-a over the field $\mathbf F_p$, where $p$ is prime.
Stopped thinking
Let X_n=(X_{n-2}+X_{n-55})\pmod m .
**Corrected Solution for Exercise 3.
**Exercise 3.
**Exercise 3.
Let $(X_n)$ be the sequence defined modulo $p^\lambda$ by X_n=x_n \pmod{p^\lambda}, \qquad 0\le n<k, and
Let $(X_n)$ be a sequence of integers modulo $m$, with period length $\lambda \gg k$, and let Algorithm B act on $(X_n)$ as described in Section 3.
In Program A of Section 3.
Let Y_n=(Y_{n-l}+Y_{n-k}) \pmod 2, \qquad 0<l<k, and suppose that every nonzero sequence satisfying this recurrence has period
Let S=(\mathbb Z_m)^k and write a state as
The recurrence is X_n=(X_{n-31}-X_{n-24})\pmod m.
Let $m = p_1 p_2 \cdots p_s$, where $p_1,\ldots,p_s$ are distinct primes.
We restart from the correct criterion and remove the unsupported construction.
Method (10) of Section 3.
Let the binary representation of $\mathrm{CONTENTS}(A_n)$ be \mathrm{CONTENTS}(A_n) = (c_{n,1} c_{n,2} \ldots c_{n,k})_2, where $c_{n,i} \in {0,1}$ for $1 \le i \le k$, and $c_{n,1}$ is the most signi...
Let $X_n$ be the binary sequence generated by method (10) with $k=35$ and CONTENTS$(A)=(a_1a_2\ldots a_{35})_2$, where $a_{35}=1,\quad a_{31}=a_{33}=a_{35}=1,\quad a_i=0 \text{ otherwise in the final...
Let $m, k \in \mathbb{Z}^+$, and define the sequence $(X_n)$ by X_1 = X_2 = \cdots = X_k = 0, and, for $n \ge 1$,
The previous solution fails because it never constructs a valid global structure linking the return-time function $q_n$ with the indexing of the base period of $X_n$, and it incorrectly treats periodi...
Let $(X_n)$ and $(Y_n)$ be integer sequences modulo $m$, with periods $\lambda_1$ and $\lambda_2$.
Let $(X_n)$ and $(Y_n)$ be sequences of integers modulo $m$ with periods $\lambda_1$ and $\lambda_2$, respectively.
The sequence is defined modulo $2^e$ by $X_{n+1} = aX_n + bX_{n-1} + c \pmod{2^e}, \qquad n \ge 1.$ The goal is to choose integers $a,b,c,X_0,X_1$ so that the resulting sequence has maximal possible p...
Let X_{n+1}=X_n+X_{n-1}\pmod{2^e} and write the state vector
Let $m = 2^e$ and consider the modified middle-square sequence defined by Coveyou: $X_0 \text{ given}, \qquad X_{n+1} = \operatorname{middle}(X_n^2 + 2^{e-1} X_n), \eqno(4)$ where the function $\opera...
Let $R_{p^r} = (\mathbb{Z}/p^r\mathbb{Z})[z]/(f(z))$ with $f(0)=1$, and denote by $\overline{z}$ the residue class of $z$ in $R_{p^r}$.