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 A131100 #13 Dec 05 2020 11:24:57
%S A131100 1,1,4,1,2,3,1,2,4,5,1,2,3,5,6,1,2,3,4,5,7,1,2,3,4,5,6,7,1,2,3,4,5,6,
%T A131100 8,10,1,2,3,4,5,6,7,8,13,1,2,3,4,5,6,8,9,10,11,1,2,3,4,5,6,7,8,9,10,
%U A131100 11,1,2,3,4,5,6,7,8,9,10,11,13
%N A131100 Indices of A002808 such that A081545(m) = Product_{k=m*(m-1)/2+1..m*(m+1)/2} A002808(a(k)).
%H A131100 Jinyuan Wang, <a href="/A131100/b131100.txt">Rows n = 1..100 of triangle, flattened</a>
%e A131100 a(2..3) = {1,4} since A081545(2) = A002808(1)*A002808(4) + 1;
%e A131100 a(7..10) = {1,2,4,5} since A081545(4) = A002808(1)*A002808(2)*A002808(4)*A002808(5) + 1.
%e A131100 Triangle begins:
%e A131100 1;
%e A131100 1, 4;
%e A131100 1, 2, 3;
%e A131100 1, 2, 4, 5;
%e A131100 1, 2, 3, 5, 6;
%e A131100 1, 2, 3, 4, 5, 7;
%e A131100 1, 2, 3, 4, 5, 6, 7;
%e A131100 ...
%Y A131100 Cf. A002808, A081545.
%K A131100 nonn,tabl
%O A131100 1,3
%A A131100 _M. F. Hasler_, Jun 14 2007
%E A131100 Offset changed to 1 by and more terms from _Jinyuan Wang_, Dec 04 2020