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 A099967 #10 Aug 03 2021 19:05:00 %S A099967 1,2,3,5,10,23,51,128,386,1092,3370,12458,43037,158638,691999,2827035, %T A099967 12150430,60980759,287737037,1414689552,8021603122,42939104470, %U A099967 237864297110,1502870474645,8999347646633,55484973357830 %N A099967 Second column of triangle in A099961. %p A099967 with(linalg):rev:=proc(a) local n, p; n:=vectdim(a): p:=i->a[n+1-i]: vector(n,p) end: ps:=proc(a) local n, q; n:=vectdim(a): q:=i->sum(a[j],j=1..i): vector(n,q) end: pss:=proc(a) local n, q; n:=vectdim(a): q:=proc(i) if i<=n then sum(a[j],j=1..i) else sum(a[j],j=1..n) fi end: vector(n+1,q) end: R[0]:=vector(1,1): for n from 1 to 31 do if n mod 3 = 0 or n mod 3 = 1 then R[n]:=ps(rev(R[n-1])) else R[n]:=pss(rev(R[n-1])) fi od: seq(R[n][2],n=2..31); # _Emeric Deutsch_, Nov 16 2004 %Y A099967 Cf. A099961, A099962, A099963. %K A099967 nonn,easy %O A099967 0,2 %A A099967 _N. J. A. Sloane_, Nov 13 2004 %E A099967 More terms from _Emeric Deutsch_, Nov 16 2004