A288152 Numbers k such that k!6 + 8 is prime, where k!6 is the sextuple factorial number (A085158 ).

3, 5, 21, 29, 41, 65, 243, 305, 389, 509, 819, 1653, 7493, 8613, 8619, 10257, 11829, 12977, 15651, 24341, 29367, 31629, 40173

Offset

1,1

Comments

Corresponding primes are: 11, 13, 8513, 623653, 894930583, 8549258359016383, ...

a(24) > 50000.

Terms > 41 correspond to probable primes.

Links

Table of n, a(n) for n=1..23.

Henri & Renaud Lifchitz, PRP Records. Search for n!6+8.

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

Example

21!6 + 8 = 21*15*9*3 + 8 = 8513 is prime, so 21 is in the sequence.

Mathematica

MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[0, 50000], PrimeQ[MultiFactorial[#, 6] + 8] &]

Crossrefs

Cf. A007661, A037082, A084438, A123910, A242994.

Sequence in context: A128561 A032414 A062225 * A082699 A096729 A001775

Adjacent sequences: A288149 A288150 A288151 * A288153 A288154 A288155

Keyword

nonn,more

Author

Robert Price, Jun 05 2017

Status

approved