A132192 - OEIS

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

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OFFSET

1,3

LINKS

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

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