A109617 Numbers k such that (10's complement factorial of k) - 1 is prime.

2, 3, 4, 7, 77, 337, 397, 566, 615, 822, 1007, 1017, 1073, 1351, 1731, 2635, 6606, 8513, 10404

Offset

1,1

Links

Table of n, a(n) for n=1..19.

Example

3 is a term because (10-3)*(10-2)*(10-1) - 1 = 503 is prime.
77 is a term because (100-77)*..*(100-10)*(10-9)*..*(10-1) - 1 is prime.

Crossrefs

Cf. A109616, A110396.

Sequence in context: A158652 A127074 A328322 * A181881 A396166 A229597

Adjacent sequences: A109614 A109615 A109616 * A109618 A109619 A109620

Keyword

nonn,base,hard,more

Author

Jason Earls, Aug 01 2005

Extensions

a(9)-a(17) from Jinyuan Wang, Aug 09 2025

a(18)-a(19) from Michael S. Branicky, Aug 13 2025

Status

approved