A109616 Numbers k such that (10's complement factorial of k) + 1 is prime.

2, 5, 10, 25, 36, 44, 65, 67, 138, 149, 176, 212, 279, 1293, 2367, 2463, 2707, 3130, 4150, 4635

Offset

1,1

Comments

Larger values not certified.

Some of the larger entries may only correspond to probable primes.

Links

Table of n, a(n) for n=1..20.

Example

a(2)=5 because (10-5)*(10-4)*(10-3)*(10-2)*(10-1) + 1 = 15121 is prime.

Mathematica

f[n_] := 10^Length[IntegerDigits[n]] - n; p = 1; Do[p *= f[n]; If[PrimeQ[p + 1], Print[n]], {n, 4635}] (* Ryan Propper, May 20 2006 *)

Crossrefs

Cf. A110396.

Sequence in context: A324149 A054866 A242935 * A181785 A018262 A336542

Adjacent sequences: A109613 A109614 A109615 * A109617 A109618 A109619

Keyword

more,nonn,base

Author

Jason Earls, Aug 01 2005

Extensions

More terms from Ryan Propper, May 20 2006

Status

approved