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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). 0
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified January 18 10:47 EST 2022. Contains 350454 sequences. (Running on oeis4.)