A177805 - OEIS

A177805

Numbers k such that k divides 15^k - 1.

1, 2, 4, 7, 8, 14, 16, 28, 32, 49, 56, 64, 98, 112, 128, 136, 196, 224, 256, 272, 343, 392, 448, 452, 512, 544, 686, 784, 812, 896, 904, 952, 1024, 1088, 1372, 1568, 1624, 1792, 1808, 1904, 2048, 2176, 2312, 2401, 2744, 3136, 3164, 3248, 3584, 3616, 3808, 4096

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

A000420 are the only odd terms of the sequence. - Robert Israel, Feb 25 2020

LINKS

Robert Israel, Table of n, a(n) for n = 1..2500

MAPLE

filter:= n -> 15 &^ n - 1 mod n = 0:

select(filter, [$1..10000]); # Robert Israel, Feb 25 2020

PROG

(PARI) is(n)=Mod(15, n)^n==1 \\ Charles R Greathouse IV, Nov 04 2016