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 A127021 #5 Mar 30 2012 17:39:18 %S A127021 1,11,80,491,2777,15120,81371,440947,2441334,13976885,83547881, %T A127021 525082654,3483272777,24413200487,180517606216,1404147099951, %U A127021 11449330342717,97521479081952,864955731435983,7966538662094103 %N A127021 Number of rhyme schemes (see reference for precise definition). %D A127021 J. Riordan, A budget of rhyme scheme counts, pp. 455 - 465 of Second International Conference on Combinatorial Mathematics, New York, April 4-7, 1978. Edited by Allan Gewirtz and Louis V. Quintas. Annals New York Academy of Sciences, 319, 1979. %H A127021 J. Riordan, <a href="/A005000/a005000.pdf">Cached copy of paper</a> %F A127021 a(k)=1. a(n)=k*a(n-1)+A000110(n-1)-A102661(n-1,k-2), k=4. %Y A127021 Cf. A005002, A005003. %K A127021 nonn %O A127021 4,2 %A A127021 _R. J. Mathar_, Jul 15 2008