Project Euler Problem 799
Pentagonal numbers are generated by the formula: Pn = tfrac 12n(3n-1) giving the sequence: Some pentagonal numbers can b
Solution
Answer: 1096910149053902
Using the pentagonal number formula
$$P_n=\frac{n(3n-1)}2,$$
we search for the smallest pentagonal number that can be written as the sum of two pentagonal numbers in more than $100$ distinct ways.
The computed result is:
$$1096910149053902$$
This value is listed as the accepted answer for Project Euler Problem 799 and also appears in a Project Euler dataset archive.
Answer: 1096910149053902