A365065 Least k such that k*M(n)*M(n+4) + 1 is prime, where M(n) = A000668(n).

20, 18, 4, 22, 112, 28, 28, 52, 28, 616, 1288, 1342, 9988, 214, 7666, 3328, 21658, 18988, 6868, 22824, 10746, 3388, 59256

Offset

1,1

Comments

If they exist, a(23) > 40809, a(24) > 2495, a(25) > 1473.

Links

Table of n, a(n) for n=1..23.

Mathematica

Table[k=1; Monitor[Parallelize[While[True, If[PrimeQ[k*(2^MersennePrimeExponent[n]-1)*(2^(MersennePrimeExponent[n+4])-1)+1], Break[]]; k++]; k], k], {n, 1, 20}]

Crossrefs

Cf. A000668 (Mersenne primes), A098917, A365063, A365064.

Sequence in context: A375787 A327788 A376974 * A076119 A004509 A248942

Adjacent sequences: A365062 A365063 A365064 * A365066 A365067 A365068

Keyword

nonn,more

Author

J.W.L. (Jan) Eerland, Aug 19 2023

Extensions

a(23) from J.W.L. (Jan) Eerland, Jan 01 2024

Status

approved