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 A038299 #9 Jul 08 2025 22:18:22
%S A038299 1,9,9,81,162,81,729,2187,2187,729,6561,26244,39366,26244,6561,59049,
%T A038299 295245,590490,590490,295245,59049,531441,3188646,7971615,10628820,
%U A038299 7971615,3188646,531441,4782969,33480783,100442349,167403915
%N A038299 Triangle whose (i,j)-th entry is binomial(i,j)*9^(i-j)*9^j.
%D A038299 B. N. Cyvin et al., Isomer enumeration of unbranched catacondensed polygonal systems with pentagons and heptagons, Match, No. 34 (Oct 1996), pp. 109-121.
%F A038299 Row sums: sum_{j=0..i} T(i,j) = A001027(i). [From _R. J. Mathar_, Mar 30 2009]
%K A038299 nonn,tabl,easy
%O A038299 0,2
%A A038299 _N. J. A. Sloane_