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 A002630 M2032 N0804 #25 May 06 2024 08:23:22
%S A002630 0,0,0,1,2,12,71,481,3708,32028,306723,3228804,37080394,461569226,
%T A002630 6192527700,89102492915,1369014167140,22373840093040,387602212164321,
%U A002630 7095737193164187,136885937242792752,2775675888994318366,59023506305591628101,1313445236142071926488
%N A002630 Number of permutations of length n with two 3-sequences.
%D A002630 D. M. Jackson, J. W. Reilly, Permutations with a prescribed number of $p$-runs. Ars Combinatoria 1 (1976), no. 1, 297-305.
%D A002630 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A002630 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A002630 J. Riordan, <a href="http://projecteuclid.org/euclid.bams/1183507357">Permutations without 3-sequences</a>, Bull. Amer. Math. Soc., 51 (1945), 745-748.
%t A002630 nmax = 22;
%t A002630 CoefficientList[Sum[((m + 2)*(m + 1)*(m + 2)!/2*(x^6*(1 - x)^4/(1 - x^3)^4) + (m + 1)*(m + 1)!*(x^4*(1 + x)*(1 - x)^3)/(1 - x^3)^3)*((x - x^3)/(1 - x^3))^m, {m, 0, nmax}]/x + O[x]^nmax, x] (* _Jean-François Alcover_, May 06 2024, after _Tani Akinari_ *)
%o A002630 (PARI) concat([0,0,0],Vec(sum(m=0,100,((m+2)*(m+1)*(m+2)!/2*(x^6*(1-x)^4/(1-x^3)^4)+(m+1)*(m+1)!*(x^4*(1+x)*(1-x)^3)/(1-x^3)^3)*((x-x^3)/(1-x^3))^m)+O(x^100))) \\ _Tani Akinari_, Nov 08 2014
%Y A002630 Cf. A047921.
%K A002630 nonn
%O A002630 1,5
%A A002630 _N. J. A. Sloane_
%E A002630 More terms from _Max Alekseyev_, Feb 20 2010