A273869 Integers n such that floor(sqrt(n!)) (A055226(n)) is a prime number.

3, 11, 14, 53, 110, 216, 322, 364, 389

Offset: 1

Author

Salvador Cerdá, Jun 01 2016

Keywords

• nonn
• more

Comments

a(10) (if it exists) requires n > 4800.

No further terms <= 15000. - Eric M. Schmidt, Jun 05 2017

Examples

			3 is in the sequence because floor(sqrt(3!)) = 2 is prime.
11 is in the sequence because floor(sqrt(11!)) = 6317 is prime.
14 is in the sequence because floor(sqrt(14!)) = 295259 is prime.
4 is not in the sequence because floor(sqrt(4!)) = 2^2.
		

Crossrefs

Cf. A055226.

Programs

Mathematica

Select[Table[n, {n, 1, 2500}], PrimeQ[Floor[Sqrt[#!]]] &]

PARI

isok(n) = isprime(sqrtint(n!)); \\ Michel Marcus, Jun 10 2016

PARI

lista(nn) = for(n=1, nn, if(ispseudoprime(sqrtint(n!)), print1(n, ", "))); \\ Altug Alkan, Jul 09 2016