MathDB
Putnam 2000 A1

Source:

September 6, 2011
PutnamLaTeXfunctioninequalitiesgeometric seriescollege contestsPutnam inequalities

Problem Statement

Let AA be a positive real number. What are the possible values of j=0xj2,\displaystyle\sum_{j=0}^{\infty} x_j^2, given that x0,x1,x_0, x_1, \cdots are positive numbers for which j=0xj=A\displaystyle\sum_{j=0}^{\infty} x_j = A?