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

150401, 13628801, 136288001, 113076743680001

Offset

1,1

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

Links

Table of n, a(n) for n=1..4.

Example

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

Mathematica

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

Prog

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

Crossrefs

Cf. A089764, A381040 (corresponding k).

Sequence in context: A254239 A051651 A065324 * A138264 A343679 A246285

Adjacent sequences: A262192 A262193 A262194 * A262196 A262197 A262198

Keyword

nonn,base

Author

Altug Alkan, Sep 14 2015

Status

approved