A289755 Primes of the form k!9-1, where k!9 is the nonuple factorial number (A114806).

2, 3, 5, 7, 89, 439, 1609, 4373, 22679, 5445439, 152681759, 17893715839, 101636305971199, 12652843234348799, 266565181393279999, 4929089879840974847999, 16401565050020468398079999, 2263415976902824638935039999, 1692607074564424130419507199999

Offset: 1

Author

Robert Price, Jul 11 2017

Keywords

• nonn

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..41 (Terms 1 through 33 from Robert Price)
• Henri & Renaud Lifchitz, PRP Records. Search for k!9-1.
• Joe McLean, Interesting Sources of Probable Primes
• OpenPFGW Project, Primality Tester

Crossrefs

Cf. A204659.

Programs

Mathematica

MultiFactorial[n_, k_] := If[n<1, 1, n*MultiFactorial[n-k, k]];
Select[Table[MultiFactorial[i, 9] - 1, {i, 2, 100}], PrimeQ[#]&]
Select[Table[Times@@Range[n,1,-9]-1,{n,200}],PrimeQ] (* Harvey P. Dale, Sep 12 2019 *)