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 A279200 #12 Jan 10 2017 11:06:15 %S A279200 1,2,20,504,21032,1293418 %N A279200 Number of square permutations of 2n things. %H A279200 Samuele Giraudo, S. Vialette, <a href="https://arxiv.org/abs/1601.05962">Unshuffling Permutations</a>, arXiv preprint arXiv:1601.05962 [cs.DS], 2016. %e A279200 The 20 square permutations of order 4 are 1234, 1243, 1423, 1324, 1342, 4132, 3124, 3142, 3412, 4312, 2134, 2143, 2413, 4213, 2314, 2431, 4231, 3241, 3421, 4321. %Y A279200 Cf. A191755 (square binary words). %K A279200 nonn,more %O A279200 0,2 %A A279200 _N. J. A. Sloane_, Dec 15 2016