Saturday, April 16, 2011

Pentagonal numbers

Triangular number

Prove that every pentagonal number greater than one can be written as the sum of three triangular numbers, two of which are equal.

Triangular numbers T_n are positive integers of the form n(n + 1)/2

Pentagonal numbers P_n are positive integers of the form n(3n - 1)/2


@matthen2 posted a picture proof http://twitpic.com/4li960

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