A298702 Numbers k such that k!+1 reversed is a prime.

1, 2, 3, 6, 11, 15, 17, 19, 22, 51, 867, 1909, 9641

Offset: 1

Author

Paolo Galliani, Jan 25 2018

Keywords

• nonn
• base
• more

Comments

a(14) > 19200, if it exists. - Giovanni Resta, May 04 2018

Crossrefs

Cf. A002981.

Programs

Mathematica

Do[If[PrimeQ[FromDigits[Reverse[IntegerDigits[n! + 1]]]], Print[n]], {n, 400}] (* Vincenzo Librandi, Jan 25 2018 *)

PARI

isok(n) = isprime(fromdigits(Vecrev(digits(n!+1)))); \\ Michel Marcus, Jan 26 2018

Extensions

a(1)-a(3) and a(8)-a(10) from Vincenzo Librandi, Jan 25 2018

a(11)-a(12) from Paolo Galliani, May 02 2018

a(13) from Giovanni Resta, May 04 2018