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 A001890 M4696 N2005 #30 Jan 12 2018 23:50:55
%S A001890 1,10,34,206,1351,10543,92708,912884,9917445,117838808,1519483258,
%T A001890 21128310078,315093762147,5016410089130,84909414423784,
%U A001890 1522548805068310,28830824064870329,574880701875755325,12039866150973004846,264230694283295736788,6063848537910027941323
%N A001890 Hit polynomials.
%D A001890 J. Riordan, The enumeration of permutations with three-ply staircase restrictions, unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963. (See A001883)
%D A001890 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A001890 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A001890 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 (unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963)
%t A001890 (* Program not suitable to compute more than a dozen terms *)
%t A001890 M[n_] := Table[If[0 <= i - j <= 2, x, 1], {i, 1, n}, {j, 1, n}];
%t A001890 a[n_] := Coefficient[Permanent[M[n]], x, 3];
%t A001890 Table[an = a[n]; Print[n, " ", an]; an, {n, 3, 15}] (* _Jean-François Alcover_, Jan 12 2018 *)
%Y A001890 Fourth column of A080061.
%Y A001890 Cf. A001883-A001891.
%K A001890 nonn
%O A001890 3,2
%A A001890 _N. J. A. Sloane_
%E A001890 More terms from _Vladeta Jovovic_, _Vladimir Baltic_, Jan 23 2003
%E A001890 a(21)-a(23) from _Vaclav Kotesovec_, Oct 10 2017