A120395 Let p(1) = 13. Then a(n) is the least k such that p(n+1) = (k*p(n))^2 + k*p(n) - 1 is prime.

1, 1, 4, 4, 10, 1, 351, 240, 620, 1362, 2184, 46, 2944

Offset

1,3

Comments

p sequence starts 181, 32941, 17361883459, 4822959955971812408731, ...

a(13) corresponds to a 12,272-digit BPSW-probable prime. - Charles R Greathouse IV, Apr 22 2012

Links

Table of n, a(n) for n=1..13.

Prog

(PARI) p=13; for(i=1, 9, k=1; while(!ispseudoprime(t=(k*p)^2+k*p-1), k++); p=t; print1(k", ")) \\ Charles R Greathouse IV, Apr 20 2012

Crossrefs

Sequence in context: A091016 A198025 A205549 * A321078 A160723 A255486

Adjacent sequences: A120392 A120393 A120394 * A120396 A120397 A120398

Keyword

nonn

Author

Pierre CAMI, Jul 01 2006

Extensions

a(9)-a(12) from Charles R Greathouse IV, Apr 20 2012

a(13) from Charles R Greathouse IV, Apr 22 2012

Status

approved