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 A047133 #7 Jan 20 2020 07:57:33 %S A047133 1,2,5,14,28,84,272,1679,5564,19613,70504,311534,1172750,4405073, %T A047133 16581264,67108040,260573610,1004778126,3867996120,15289911196, %U A047133 59854486782,233437968413,909025875014,3575067252387,14038457059264 %N A047133 T(n,n-1), array T as in A047130. %K A047133 nonn %O A047133 1,2 %A A047133 _Clark Kimberling_ %E A047133 Definition corrected by _Georg Fischer_, Jan 20 2020