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 A184273 #18 Oct 31 2017 21:04:55
%S A184273 10,76,700,8296,104968,1399176,19175140,268447816,3817763740,
%T A184273 54975738736,799645010860,11728126132976,173215372864600,
%U A184273 2573485530115576,38430716856090160,576460752706084936,8680820741074491040,131176846752106589576,1988364834899715824380
%N A184273 Number of distinct n X 2 toroidal 0..3 arrays.
%H A184273 Andrew Howroyd, <a href="/A184273/b184273.txt">Table of n, a(n) for n = 1..100</a>
%t A184273 T[n_, k_] := (1/(n*k))*Sum[Sum[EulerPhi[c]*EulerPhi[d]*4^(n*k/LCM[c, d]), {d, Divisors[k]}], {c, Divisors[n]}]; a[n_] := T[n, 2]; Array[a, 20] (* _Jean-François Alcover_, Oct 31 2017, after _Andrew Howroyd_ *)
%Y A184273 Column 2 of A184277.
%K A184273 nonn
%O A184273 1,1
%A A184273 _R. H. Hardin_, Jan 10 2011
%E A184273 Terms a(13) and beyond from _Andrew Howroyd_, Sep 27 2017