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 A187123 #8 Oct 15 2024 18:51:56
%S A187123 1,4,22,164,1599,19624,292799,5162063,105139954,2430528374,
%T A187123 62877375426,1799698534522,56461862815496,1926534563625822,
%U A187123 71024188655886038,2813193432059656268,119136308527407025379,5371507426340905440926
%N A187123 Row sums of triangle A187120.
%C A187123 Definition of triangle: A187120(n,k) = [y^k] R_{n-1}(y+y^2) for k=3..n, n>3, where R_n(y) is the n-th row polynomial starting with R_3(y)=y^3.
%o A187123 (PARI) {a(n)=local(Rn=y^3);for(m=3,n-1,Rn=subst(truncate(Rn),y,y+y^2+O(y^m)));subst(truncate(Rn),y,1)}
%Y A187123 Cf. A187120, A135083, A187121, A187122, A187124.
%K A187123 nonn
%O A187123 3,2
%A A187123 _Paul D. Hanna_, Mar 08 2011