login
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
OFFSET
1,6
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
KEYWORD
nonn
AUTHOR
Creighton Dement, Jun 11 2009
STATUS
approved