A156707 For all numbers k(n) congruent to +1 or -1 (mod 4) starting with k(n) = {3,5,7,9,11,...}, a(k(n)) is the congruence (mod 4) if k(n) is prime and 0 if k(n) is composite.

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

Offset

1,1

Comments

Expression for k(n): k(n) = 4*ceiling(n/2) + (-1)^n, so the parity of n gives us the congruence (mod 4) of k(n). - Daniel Forgues, Mar 01 2009

Links

Daniel Forgues, Table of n, a(n) for n = 1..49999

Crossrefs

The absolute values of this sequence give A101264 (for n > 0.) The partial sums of this sequence give A156749. - Daniel Forgues, Mar 01 2009

Sequence in context: A087755 A050072 A267576 * A131309 A267208 A106510

Adjacent sequences: A156704 A156705 A156706 * A156708 A156709 A156710

Keyword

sign

Author

Daniel Forgues, Feb 13 2009, Feb 14 2009

Status

approved