A156706 For all numbers k(n) congruent to +1 or -1 (mod 6) starting with k(n) = {5,7,11,13,...}, a(k(n)) is the congruence (mod 6) if k(n) is prime and 0 if k(n) is composite.

-1, 1, -1, 1, -1, 1, -1, 0, -1, 1, 0, 1, -1, 1, -1, 0, -1, 0, -1, 1, 0, 1, -1, 1, 0, 1, -1, 0, -1, 0, 0, 1, -1, 1, -1, 1, -1, 0, 0, 0, 0, 1, -1, 0, -1, 1, 0, 0, -1, 1, 0, 1, 0, 1, -1, 0, -1, 0, -1, 1, 0, 0, -1, 1, -1, 1, 0, 0, 0, 1, 0, 0, 0, 1, -1, 1, -1, 0, -1, 1, 0, 0, -1, 0, -1, 0, -1, 0, -1, 1, 0

Offset: 1

Author

Daniel Forgues, Feb 13 2009, Feb 14 2009

Keywords

• sign

Comments

Expression for k(n): k(n) = 6*ceiling(n/2) + (-1)^n, so the parity of n gives us the congruence (mod 6) of k(n). - Daniel Forgues, Mar 01 2009

Links

• Daniel Forgues, Table of n, a(n) for n = 1..33332

Crossrefs

Cf. A075743.

The absolute values of this sequence give A075743. The partial sums of this sequence give A156709.