A045580 Numbers k that divide 7^k + 2^k.

1, 3, 9, 27, 39, 81, 117, 171, 243, 351, 507, 513, 729, 1053, 1521, 1539, 2187, 2223, 3081, 3159, 3249, 4563, 4617, 5109, 6123, 6561, 6591, 6669, 9243, 9477, 9747, 13689, 13851, 15327, 18153, 18369, 19683, 19773, 20007, 27729, 28431, 28899, 29241, 39159, 40053

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..2000

Crossrefs

Cf. A074602.

Programs

Mathematica

Select[Range[30000], Divisible[PowerMod[2, #, #] + PowerMod[7, #, #], #] &] (* Amiram Eldar, Oct 23 2021 *)