A089131 Primes of the form (k! + 3)/3.

3, 41, 241, 13441, 13305601, 118562476032001, 8617338912961658880001, 123997775596633739155999816050278400000001

Offset: 1

Author

Cino Hilliard, Dec 05 2003

Keywords

• nonn

Comments

The next term is too large to include.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..13

Crossrefs

Cf. A089085, A139150.

Programs

Magma

[a: n in [1..50] | IsPrime(a) where a is (Factorial(n)+3) div 3]; // Vincenzo Librandi, Dec 12 2011

Mathematica

Select[Table[(n!+3)/3,{n,0,50}],PrimeQ] (* Vincenzo Librandi, Dec 12 2011 *)

PARI

nfactp2d2(n) = { for(x=1,n, y=floor((x!+ 3)/3); if(isprime(y),print1(y",")) ) }

Formula

a(n) = A139150(A089085(n)). - Amiram Eldar, Oct 13 2024