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 A220904 #11 Feb 02 2020 21:36:12 %S A220904 1,1,2,8,336,356788059,607158046495120886820621 %N A220904 Number of equivalence classes of perfect matchings in the n-cube. %H A220904 N. Graham and F. Harary, <a href="https://doi.org/10.1016/0893-9659(88)90173-5">The number of perfect matchings in a hypercube</a>, Appl. Math. Lett., 1 (1988), 45-48. %H A220904 Patric R. J. Östergård and V. H. Pettersson, <a href="https://doi.org/10.1007/s11083-012-9279-8">Enumerating Perfect Matchings in n-Cubes</a>, Order, November 2013, Volume 30, Issue 3, pp 821-835. %H A220904 Ville Pettersson, <a href="https://aaltodoc.aalto.fi/bitstream/handle/123456789/17688/isbn9789526063652.pdf?sequence=1">Graph Algorithms for Constructing and Enumerating Cycles and Related Structures</a>, Preprint 2015. %Y A220904 Cf. A005271. %K A220904 nonn %O A220904 1,3 %A A220904 _N. J. A. Sloane_, Jan 01 2013