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 A001884 M2117 N0835 #26 Dec 23 2021 22:47:54 %S A001884 1,0,1,2,20,104,775,6140,55427,553802,6087992,72994152,948103477, %T A001884 13262133736,198769630061,3177862894922,53984653965996, %U A001884 971068821144112,18438722595913195,368558842844143268,7735520783692157215,170095060428041137778,3910332719957508452016,93806427360751009531632 %N A001884 Hit polynomials. %D A001884 J. Riordan, The enumeration of permutations with three-ply staircase restrictions, unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963. See A001883. %D A001884 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). %D A001884 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A001884 N. J. A. Sloane, <a href="/A001883/a001883_21.pdf">Annotated copy of Riordan's Three-Ply Staircase paper</a> (unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963) %Y A001884 Second column of A080018. %Y A001884 Cf. A001883-A001891. %K A001884 nonn %O A001884 1,4 %A A001884 _N. J. A. Sloane_ %E A001884 More terms from _Vladeta Jovovic_ and _Vladimir Baltic_, Jan 20 2003 %E A001884 a(21)-a(24) from _Vaclav Kotesovec_, Oct 10 2017