A288371 Primes of the form k!9 + 1, where k!9 is the nonuple factorial number (A114806).

2, 3, 5, 7, 11, 23, 37, 53, 71, 113, 137, 163, 191, 757, 2161, 2801, 51521, 1418561, 4093601, 42456961, 69509441, 105616001, 2420046721, 9160905601, 1270453824641, 2326680294401, 190787784140801, 509498986796801, 2805949277824001, 612940220628736001

Offset: 1

Author

Robert Price, Jun 08 2017

Keywords

• nonn

Links

• Robert Price, Table of n, a(n) for n = 1..55
• OpenPFGW Project, Primality Tester.

Crossrefs

Cf. A114806, A204660.

Programs

Mathematica

MultiFactorial[n_, k_] := If[n<1, 1, n*MultiFactorial[n-k, k]];
Select[Table[MultiFactorial[i, 9] + 1, {i, 0, 100}], PrimeQ[#]&]

Formula

a(n) = 1 + A114806(A204660(n+1)). - Elmo R. Oliveira, Feb 26 2025