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 A298012 #7 Jan 11 2018 00:10:31 %S A298012 0,0,1,1,4,16,85,533,3888,32268,300193,3093377,34970468,430293488, %T A298012 5724411845,81871668773,1252691817856,20417647146396,353169795861921, %U A298012 6461418976274657,124664729763630436 %N A298012 a(0)=a(1)=0; thereafter a(n) = A162973(n)/(n-1). %H A298012 John Riordan, <a href="/A002720/a002720_3.pdf">Letter to N. J. A. Sloane, Sep 26 1980 with notes on the 1973 Handbook of Integer Sequences</a>. Note that the sequences are identified by their N-numbers, not their A-numbers. %F A298012 Riordan gives a recurrence. %K A298012 nonn %O A298012 0,5 %A A298012 _N. J. A. Sloane_, Jan 10 2018