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 A004206 M2381 #19 Oct 24 2023 20:46:02 %S A004206 3,4,25,108,735,5248,40824,362000,3628185,39045888,478988081, %T A004206 6227101888,87146087625,1314459353088,20922788404479,355737629952000, %U A004206 6402373698206889,121479069952000000 %N A004206 Number of permutations of length n with spread 2. %D A004206 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A004206 R. L. Graham and D. H. Lehmer, <a href="https://doi.org/10.1017/S1446788700019339">On the Permanent of Schur's Matrix</a>, Jour. Australian Math. Soc. 21 no. 4 (series A) (1976), 487-497. %K A004206 nonn %O A004206 3,1 %A A004206 _N. J. A. Sloane_ %E A004206 More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), May 17 2007