Bounded by a Hidden Sine

7/10complex numberssequences

Problem

A sequence satisfies a0=0a_0 = 0, a1=13a_1 = \dfrac13, and

3an+14an+3an1=0(n1).3a_{n+1} - 4a_n + 3a_{n-1} = 0 \qquad (n \ge 1).

Prove that an<12|a_n| < \dfrac12 for every positive integer nn.

Answer

Solution

Difficulty7/10
Topicscomplex numbers, sequences

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