A132192 Least number k such that 4*(k*(2^p-1))^2 + 1 is prime where 2^p-1 is a Mersenne prime (p in A000043).

1, 1, 2, 6, 40, 17, 4, 6, 47, 48, 334, 99, 585, 19, 350, 1201, 197, 3577, 2020, 870, 2322, 4488, 6150, 12397, 7817

Offset

1,3

Links

Table of n, a(n) for n=1..25.

Example

a(1) = 1 since 3 = 2^A000043(1) - 1 and 4*(1*3)^2 + 1 = 37 is prime.

Mathematica

f[n_] := Module[{k = 1}, While[!PrimeQ[4*(k*n)^2 + 1], k++]; k]; f /@ (2^MersennePrimeExponent[Range[15]] - 1)(* Amiram Eldar, Jul 17 2021 *)

Crossrefs

Cf. A000043, A000668.

Sequence in context: A295912 A120492 A028300 * A340299 A068207 A331702

Adjacent sequences: A132189 A132190 A132191 * A132193 A132194 A132195

Keyword

nonn,more

Author

Pierre CAMI, Nov 05 2007

Extensions

Data corrected and a(23)-a(25) added by Amiram Eldar, Jul 17 2021

Status

approved