A139060 Primes of the form (4+k!)/4.

7, 31, 181, 1556755201, 12772735542927360001, 3877802510832746496000001, 65782709233423382541804503040000001, 203978820811974433586402817399028973568000000001

Offset: 1

Author

Artur Jasinski, Apr 07 2008

Keywords

• nonn

Comments

For numbers k for which (4+k!)/4 is prime see A139061.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..15

Crossrefs

Cf. A007749, A020458, A082672, A089085, A089130, A117141, A139056, A139057, A139058, A139059, A139061, A139062, A139063, A139064, A139065, A139066, A139151.

Programs

Mathematica

a = {}; Do[If[PrimeQ[(n! + 4)/4], AppendTo[a, (n! + 4)/4]], {n, 1, 50}]; a
Select[(4+Range[100]!)/4,PrimeQ] (* Harvey P. Dale, Oct 05 2016 *)

PARI

for(k=4,1e3,if(ispseudoprime(t=k!/4+1),print1(t", "))) \\ Charles R Greathouse IV, Jul 15 2011

Formula

a(n) = A139151(A139061(n)). - Amiram Eldar, Oct 13 2024