A202422 Primes of the form n!*n!! + 1.

2, 5, 19, 193, 1801, 56240459218944001, 112873711099106889552388221969528619131820978659655680000000000001

Offset

1,1

Comments

For n > 4, the last digits of the prime numbers are of the form 01, 001, 0000000000001,...,...000001.

Generated by n = 1, 2, 3, 4, 5, 14, 37, 48, 50, 52,... - R. J. Mathar, Dec 21 2011

The next term (a(8)) has 93 digits. - Harvey P. Dale, Jun 13 2022

Links

Table of n, a(n) for n=1..7.

Example

19 is in the sequence because, for n = 3, 3!*3!! + 1 = 6*3 + 1 = 19.

Mathematica

a={}; Do[p=n!*n!!+1; If[PrimeQ[p], AppendTo[a, p]], {n, 10^3}]; Print[a];
Select[Table[n! n!!+1, {n, 40}], PrimeQ] (* Harvey P. Dale, Jun 13 2022 *)

Crossrefs

Cf. A000142, A006882.

Sequence in context: A108799 A193674 A085871 * A212269 A359116 A080280

Adjacent sequences: A202419 A202420 A202421 * A202423 A202424 A202425

Keyword

nonn

Author

Michel Lagneau, Dec 19 2011

Status

approved