MathDB
Aime 2004 #7 - coefficient in expansion

Source:

July 31, 2005
AMCAIME

Problem Statement

Let CC be the coefficient of x2x^2 in the expansion of the product (1x)(1+2x)(13x)(1+14x)(115x).(1 - x)(1 + 2x)(1 - 3x)\cdots(1 + 14x)(1 - 15x). Find C|C|.