A287914 Numbers k such that k!6 + 4 is prime, where k!6 is the sextuple factorial number (A085158 ).

1, 3, 7, 9, 11, 15, 19, 27, 35, 59, 71, 75, 95, 109, 153, 155, 169, 189, 277, 355, 383, 405, 455, 625, 843, 853, 879, 1389, 1423, 1515, 1871, 2059, 2677, 3095, 4473, 5691, 5927, 8149, 10789, 12171, 14683, 26383, 34227, 40945

Offset

1,2

Comments

Corresponding primes are: 5, 7, 11, 31, 59, 409, 1733, 229639, 21827579, ...

a(45) > 50000.

Terms > 35 correspond to probable primes.

Links

Table of n, a(n) for n=1..44.

Henri & Renaud Lifchitz, PRP Records. Search for n!6+4.

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

Example

11!6 + 4 = 11*5 + 4 = 59 is prime, so 11 is in the sequence.

Mathematica

MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[0, 50000], PrimeQ[MultiFactorial[#, 6] + 4] &]

Crossrefs

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

Sequence in context: A125667 A072939 A171947 * A291348 A186890 A248667

Adjacent sequences: A287911 A287912 A287913 * A287915 A287916 A287917

Keyword

nonn,more

Author

Robert Price, Jun 02 2017

Status

approved