project-euler

Triangular, pentagonal, and hexagonal

Problem Description

Triangle, pentagonal, and hexagonal numbers are generated by the following formulae:

     
Triangle Tn=n(n+1)/2 1, 3, 6, 10, 15, …
Pentagonal Pn=n(3n-1)/2 1, 5, 12, 22, 35, …
Hexagonal Hn=n(2n-1) 1, 6, 15, 28, 45, …

It can be verified that T285 = P165 = H143 = 40755.

Find the next triangle number that is also pentagonal and hexagonal.

Performance

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Real time: 0.429 s
User time: 0.348 s
Sys. time: 0.126 s
CPU share: 110.67 %
Exit code: 0