A262195 Primes that are the concatenation of 1, k! and 1, for some integer k.

150401, 13628801, 136288001, 113076743680001

Offset: 1

Author

Altug Alkan, Sep 14 2015

Keywords

• nonn
• base

Comments

Inspired by A089764.

The next term is associated with k = 21225 and has 82625 digits, so it is too large to include here. See A381040. - Michael S. Branicky, Apr 15 2025

Examples

			For n = 1, k = 7, 7! = 5040, and a(1) = 150401 is a prime number.
		

Crossrefs

Cf. A089764, A381040 (corresponding k).

Programs

Magma

[m: n in [1..1000] | IsPrime(m) where m is Seqint(Intseq(1) cat Intseq(Factorial(n)) cat Intseq(1))]; // Vincenzo Librandi, Sep 15 2015

Mathematica

Select[Table[FromDigits[Flatten[{(1), IntegerDigits[n!], {1}}]], {n, 1000}], PrimeQ] (* Vincenzo Librandi, Sep 15 2015 *)

PARI

for(n=1, 1e3, if(isprime(k=eval(Str(1,n!,1))), print1(k", ")))