A288885 Primes of the form k!3 + 3^9, where k!3 is the triple factorial number (A007661).

19687, 19763, 19963, 20563, 32003, 229123, 4208483, 24364003, 72642189283, 2324549446883, 5577337931669523683, 38900816605808456499219683, 26070192823309041523916819683

Offset: 1

Author

Robert Price, Jun 18 2017

Keywords

• nonn

Links

• Robert Price, Table of n, a(n) for n = 1..18
• Henri and Renaud Lifchitz, PRP Records.Search for n!3+3^9.
• Joe McLean, Interesting Sources of Probable Primes.
• OpenPFGW Project, Primality Tester.

Crossrefs

Cf. A007661, A265378.

Programs

Mathematica

MultiFactorial[n_, k_] := If[n<1, 1, n*MultiFactorial[n-k, k]];
Select[Table[MultiFactorial[i, 3] + 3^9, {i, 0, 100}], PrimeQ[#]&]
Select[Table[Times@@Range[n,1,-3]+19683,{n,100}],PrimeQ] (* Harvey P. Dale, Sep 18 2023 *)

Formula

a(n) = 19683 + A007661(A265378(n)). - Elmo R. Oliveira, Apr 14 2025