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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Expression for k(n): k(n) = 4 ceil(n/2) + (-1)^n, so the parity of n gives us the congruence (mod 4) of k(n). [From 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. [From 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

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Last modified August 17 17:08 EDT 2019. Contains 326059 sequences. (Running on oeis4.)