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 A263826 #17 Oct 10 2018 03:24:37
%S A263826 1,7,9,29,19,63,33,107,74,133,73,285,99,231,219,393,163,518,201,623,
%T A263826 393,511,289,1155,422,693,634,1101,451,1533,513,1479,897,1141,915,
%U A263826 2482,723,1407,1227,2609,883,2751,969,2477,2078,2023,1153,4569
%N A263826 The number c_{Z3 pi_1(B_1)}(2n) of 3-torus 2n-coverings over the first amphicosm.
%H A263826 Gheorghe Coserea, <a href="/A263826/b263826.txt">Table of n, a(n) for n = 1..20000</a>
%H A263826 G. Chelnokov, M. Deryagina, A. Mednykh, <a href="http://arxiv.org/abs/1502.01528">On the Coverings of Amphicosms; Revised title: On the coverings of Euclidian manifolds B_1 and B_2</a>, arXiv preprint arXiv:1502.01528 [math.AT], 2015.
%t A263826 a[n_] := 1/2 Sum[Sum[(d^2 + 5/2 + 3/2 (-1)^Mod[d, 2]) m, {m, Divisors[n/d]} ], {d, Divisors[n]}];
%t A263826 Array[a, 48] (* _Jean-François Alcover_, Oct 10 2018, after _Gheorghe Coserea_ *)
%o A263826 (PARI)
%o A263826 a(n) = 1/2 * sumdiv(n, d, sumdiv(n\d, m, (d^2 + 5/2 + 3/2*(-1)^(d%2))*m));
%o A263826 vector(48, n, a(n)) \\ _Gheorghe Coserea_, May 04 2016
%Y A263826 Cf. A263825-A263830, A263832.
%K A263826 nonn
%O A263826 1,2
%A A263826 _N. J. A. Sloane_, Oct 28 2015
%E A263826 More terms from _Gheorghe Coserea_, May 04 2016