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A161491 a(n) = number of primes p less than A000040(n) (the n-th prime) such that (p + 1)*(A000040(n) - 1) is a square 0
0, 0, 1, 1, 0, 2, 1, 2, 0, 0, 1, 1, 0, 1, 0, 0, 0, 1, 0, 0, 4, 0, 0, 0, 3, 1, 1, 0, 4, 0, 1, 0, 0, 1, 0, 4, 0, 6, 0, 0, 0, 3, 0, 5, 1, 1, 0, 0, 0, 1, 0, 0, 2, 1, 1, 0, 0, 2, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 2, 0, 0, 1, 1, 1, 0, 1, 0, 6, 0, 0, 1, 1, 0, 1, 0, 0, 6, 2, 0, 0, 0, 0, 1, 2, 0, 0, 0, 0, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

LINKS

Table of n, a(n) for n=1..105.

PROG

(PARI) forprime(q=1, 1000, my(q1=q-1, c=0); forprime(p=1, q-1, issquare((p+1)*q1)&c++); print1(c", ")) - M. F. Hasler

CROSSREFS

Sequence in context: A035186 A035194 A245818 * A332998 A301652 A030203

Adjacent sequences:  A161488 A161489 A161490 * A161492 A161493 A161494

KEYWORD

nonn

AUTHOR

Creighton Dement, Jun 11 2009

STATUS

approved

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Last modified May 19 11:44 EDT 2022. Contains 353833 sequences. (Running on oeis4.)