A139058 Numbers n such that (5+n!)/5 is prime.

7, 9, 11, 14, 19, 23, 45, 121, 131, 194, 735, 751, 1316, 1372, 2084, 2562, 5678, 5758, 12533, 24222

Offset: 1

Author

Artur Jasinski, Apr 07 2008

Keywords

• nonn

Comments

For primes of the form (5+n!)/5 see A139059.

a(21) > 25000. - Robert Price, Nov 20 2016

Crossrefs

Cf. A139059.

Cf. n!/m-1 is a prime: A002982, A082671, A139056, A139199-A139205; n!/m+1 is a prime: A002981, A082672, A089085, A139061, A139058, A139063, A139065, A151913, A137390, A139071 (1<=m<=10).

Programs

Magma

[ n: n in [5..734] | IsPrime((Factorial(n)+5) div 5) ];

Mathematica

a = {}; Do[If[PrimeQ[(n! + 5)/5], AppendTo[a, n]], {n, 1, 751}]; a

PARI

A139058(n) = local(k=(n!+5)\5); if(isprime(k), k, 0);
for(n=5, 800, if(A139058(n)>0, print1(n, ", ")))

Extensions

More terms from Serge Batalov, Feb 18 2015

a(19)-a(20) from Robert Price, Nov 20 2016