This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A045580 #19 Oct 23 2021 10:06:20 %S A045580 1,3,9,27,39,81,117,171,243,351,507,513,729,1053,1521,1539,2187,2223, %T A045580 3081,3159,3249,4563,4617,5109,6123,6561,6591,6669,9243,9477,9747, %U A045580 13689,13851,15327,18153,18369,19683,19773,20007,27729,28431,28899,29241,39159,40053 %N A045580 Numbers k that divide 7^k + 2^k. %H A045580 Amiram Eldar, <a href="/A045580/b045580.txt">Table of n, a(n) for n = 1..2000</a> %t A045580 Select[Range[30000], Divisible[PowerMod[2, #, #] + PowerMod[7, #, #], #] &] (* _Amiram Eldar_, Oct 23 2021 *) %Y A045580 Cf. A074602. %K A045580 nonn %O A045580 1,2 %A A045580 _David W. Wilson_