A262436 Number of ways to represent 2n - 1 as p^2 + q^2 + r with p, q, and r prime, and p >= q.

0, 0, 0, 0, 0, 1, 1, 2, 0, 1, 2, 1, 2, 1, 1, 3, 0, 1, 3, 2, 2, 0, 2, 2, 2, 2, 2, 4, 2, 1, 4, 3, 3, 2, 3, 3, 1, 3, 4, 4, 5, 0, 2, 5, 2, 4, 3, 2, 4, 1, 4, 3, 5, 2, 3, 5, 1, 4, 6, 2, 5, 2, 2, 4, 3, 3, 3, 5, 3, 3, 5, 2, 4, 6, 3, 3, 4, 2, 6, 6, 3, 3, 5, 3, 3, 6, 3

Offset: 1

Author

Peter Kagey, Sep 22 2015

Keywords

• nonn

Comments

k is in A212292 if and only if a((k+1)/2) = 0.

Links

• Peter Kagey, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A212292.

Formula

a(16) = 3 because there are three different ways to represent 16 * 2 - 1 = 31 in the form p^2 + q^2 + r with p, q, and r prime, and p >= q:

2^2 + 2^2 + 23,

3^3 + 3^3 + 13,

5^2 + 2^2 + 2.