A226915 Fourth column of A226518.

-1, 1, 1, 1, 1, -1, 3, -1, 1, 1, 1, -1, 3, -1, 1, 1, -1, 3, 3, 1, 1, 1, 3, -1, 1, 1, 1, 1, 1, 1, 1, -1, -1, 1, 1, -1, 3, -1, 1, 1, 3, 3, -1, 1, -1, 1, 1, 1, 1, 3, 3, 1, 1, 3, -1, 1, 1, 1, -1, -1, -1, 3, 3, -1, -1, 3, 1, 1, 1, 3, 1, 1, -1, 3, -1, 1, 1, 3, 1, 1, 3, 3, 1, 1, 1, 3, -1, 1, 1, 3, 1, 1, -1, 3, -1, 1

Offset: 3

Author

N. J. A. Sloane, Jun 22 2013

Keywords

• sign

Crossrefs

Cf. A226518.

Formula

a(n) = 1 + Legendre(2,p) + Legendre(3,p) where p = prime(n).