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 A184278 #13 Sep 27 2017 19:30:13
%S A184278 3,27,2211,2691711,33891544611,4169295457320267,
%T A184278 4883659780216684279491,53651309692070594433108320631,
%U A184278 5474401089420219382077156686715199875,5153775207320113310364632834595843483435609099,44553974378043749018508590814287728257805180848046070883
%N A184278 Number of distinct n X n toroidal 0..2 arrays.
%H A184278 Andrew Howroyd, <a href="/A184278/b184278.txt">Table of n, a(n) for n = 1..40</a>
%F A184278 a(n) = (1/(n^2)) * Sum_{c|n} Sum_{d|n} phi(c) * phi(d) * 3^(n^2/lcm(c,d)). - _Andrew Howroyd_, Sep 27 2017
%Y A184278 Diagonal of A184284.
%K A184278 nonn
%O A184278 1,1
%A A184278 _R. H. Hardin_, Jan 10 2011
%E A184278 Terms a(6) and beyond from _Andrew Howroyd_, Sep 27 2017