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Primes of the form (k! + 3)/3.
2

%I #15 Oct 14 2024 01:36:36

%S 3,41,241,13441,13305601,118562476032001,8617338912961658880001,

%T 123997775596633739155999816050278400000001

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

%C The next term is too large to include.

%H Vincenzo Librandi, <a href="/A089131/b089131.txt">Table of n, a(n) for n = 1..13</a>

%F a(n) = A139150(A089085(n)). - _Amiram Eldar_, Oct 13 2024

%t Select[Table[(n!+3)/3,{n,0,50}],PrimeQ] (* _Vincenzo Librandi_, Dec 12 2011 *)

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

%o (Magma) [a: n in [1..50] | IsPrime(a) where a is (Factorial(n)+3) div 3]; // _Vincenzo Librandi_, Dec 12 2011

%Y Cf. A089085, A139150.

%K nonn

%O 1,1

%A _Cino Hilliard_, Dec 05 2003