A287844 Numbers k such that k!6 + 3 is prime, where k!6 is the sextuple factorial number (A085158 ).

2, 4, 8, 10, 14, 16, 20, 22, 26, 34, 70, 164, 346, 398, 902, 938, 1426, 1682, 1928, 3596, 3796, 15058, 25654, 37330

Offset

1,1

Comments

Corresponding primes are: 5, 7, 19, 43, 227, 643, 4483, 14083, 116483, 13404163, ...

a(25) > 50000.

Terms > 34 correspond to probable primes.

Links

Table of n, a(n) for n=1..24.

Henri & Renaud Lifchitz, PRP Records. Search for n!6+3.

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

Example

10!6 + 3 = 10*4 + 3 = 43 is prime, so 10 is in the sequence.

Mathematica

MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[0, 50000], PrimeQ[MultiFactorial[#, 6] + 3] &]

Crossrefs

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

Sequence in context: A047235 A328588 A356435 * A219696 A087505 A086801

Adjacent sequences: A287841 A287842 A287843 * A287845 A287846 A287847

Keyword

nonn,more

Author

Robert Price, Jun 01 2017

Status

approved