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 A056645 #3 Mar 30 2012 17:30:26
%S A056645 1,2,3,9,14,27,81,98,99,153,243,621,686,729,1199,2187,4018,4802,5049,
%T A056645 6561,8019,12393,19683,20541,31509,33614,59049,70389,82377,113974,
%U A056645 150903,177147,226557,235298,299619,308014,340443,408969,423929,531441
%N A056645 Numbers n such that n | 3^n + 2^n + 1^n.
%t A056645 Do[ If[ Mod[ PowerMod[ 3, n, n ] + PowerMod[ 2, n, n ] + 1, n ] == 0, Print[ n ] ], {n, 1, 10^6} ]
%Y A056645 Cf. A001550.
%K A056645 nonn
%O A056645 1,2
%A A056645 _Robert G. Wilson v_, Aug 25 2000