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 A184285 #18 Nov 01 2017 12:23:17
%S A184285 15,175,2635,49075,976887,20349075,435970995,9536816575,211927736135,
%T A184285 4768373047015,108372083629275,2483526896194175,57312158484825735,
%U A184285 1330460821533203275,31044085821533856483,727595761432647754075,17119900268689323874095
%N A184285 Number of distinct n X 2 toroidal 0..4 arrays.
%H A184285 Andrew Howroyd, <a href="/A184285/b184285.txt">Table of n, a(n) for n = 1..100</a>
%t A184285 T[n_, k_] := (1/(n*k))*Sum[Sum[EulerPhi[c]*EulerPhi[d]*5^(n*k/LCM[c, d]), {d, Divisors[k]}], {c, Divisors[n]}]; a[n_] := T[n, 2]; Array[a, 17] (* _Jean-François Alcover_, Nov 01 2017, after _Andrew Howroyd_ *)
%o A184285 (PARI) a(n) = my(k=2); (1/(n*k)) * sumdiv(n, c, sumdiv(k, d, eulerphi(c) * eulerphi(d) * 5^(n*k/lcm(c, d)))); \\ _Michel Marcus_, Nov 01 2017
%Y A184285 Column 2 of A184288.
%K A184285 nonn
%O A184285 1,1
%A A184285 _R. H. Hardin_, Jan 10 2011
%E A184285 Terms a(12) and beyond from _Andrew Howroyd_, Sep 27 2017