A289861 Primes of the form k!10 - 2, where k!10 is the decuple factorial number (A288327).

2, 3, 5, 7, 37, 73, 229, 1873, 4957, 7159, 29599, 293599, 2953123, 9476647, 1643049664639, 30501459767616059381067752838134765623, 75901465778001946800870398616055887199, 168354282831355577455162448188672669399, 73004868196707960876168803928840928829809

Offset: 1

Author

Robert Price, Jul 13 2017

Keywords

• nonn

Links

• Robert Price, Table of n, a(n) for n = 1..32
• Henri and Renaud Lifchitz, PRP Records.Search for n!10-2.
• Joe McLean, Interesting Sources of Probable Primes.
• OpenPFGW Project, Primality Tester.

Crossrefs

Cf. A283559, A288327.

Programs

Mathematica

MultiFactorial[n_, k_] := If[n<1, 1, n*MultiFactorial[n-k, k]];
Select[Table[MultiFactorial[i, 10] - 2, {i, 3, 100}], PrimeQ[#]&]
Select[Table[Times@@Range[n,1,-10]-2,{n,300}],PrimeQ] (* Harvey P. Dale, Sep 09 2021 *)

Formula

a(n) = A288327(A283559(n)) - 2. - Elmo R. Oliveira, Feb 25 2025