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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.
4
-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
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
KEYWORD
sign
AUTHOR
Daniel Forgues, Feb 13 2009, Feb 14 2009
STATUS
approved