A159482 Greatest odd prime q < 2*n such that p < q and p prime and p = 2*n - q or 0 if no such prime exists.

0, 0, 0, 5, 7, 7, 11, 13, 13, 17, 19, 19, 23, 23, 23, 29, 31, 31, 31, 37, 37, 41, 43, 43, 47, 47, 47, 53, 53, 53, 59, 61, 61, 61, 67, 67, 71, 73, 73, 73, 79, 79, 83, 83, 83, 89, 89, 89, 79, 97, 97, 101, 103, 103, 107, 109, 109, 113, 113, 113, 109, 113, 113, 109, 127, 127

Offset: 1

Author

Pierre CAMI, Apr 14 2009

Keywords

• nonn

Comments

q + p = 2*n and p*q = ((q+p)/2)^2 - ((q-p)/2)^2 = n^2 - ((q-p)/2)^2.

Essentially the same as A020482. - R. J. Mathar, Oct 24 2009

Links

• Pierre CAMI, Table of n, a(n) for n = 1..55000