A288878 Primes of the form k!3 + 3^2, where k!3 is the triple factorial number (A007661).

11, 13, 19, 37, 89, 12329, 209449, 1106569, 24344329, 96342409, 2504902409, 17961239296009, 52580450364682240009, 2295148179742698933452800009, 7825229077844441903818866688000009, 145302140752338100885902776123355299840000009

Offset: 1

Author

Robert Price, Jun 18 2017

Keywords

• nonn

Links

• Robert Price, Table of n, a(n) for n = 1..24
• Henri and Renaud Lifchitz, PRP Records.Search for n!3+3^2.
• Joe McLean, Interesting Sources of Probable Primes.
• OpenPFGW Project, Primality Tester.

Crossrefs

Cf. A007661, A247865.

Programs

Mathematica

MultiFactorial[n_, k_] := If[n<1, 1, n*MultiFactorial[n-k, k]];
Select[Table[MultiFactorial[i, 3] + 3^2, {i, 0, 100}], PrimeQ[#]&]

Formula

a(n) = 9 + A007661(A247865(n)). - Elmo R. Oliveira, Apr 13 2025