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 A173111 #5 Jun 02 2025 02:41:12 %S A173111 1,1,2,1,5,1,15,2,3,52,5,3,203,15,6,6,877,52,15,6,4140,203,45,12,20, %T A173111 21147,877,156,30,20,115975,4140,609,90,40,60,678570,21147,2631,312, %U A173111 100,60 %N A173111 Triangle read by rows, A173108 * the diagonalized variant of A173110. %C A173111 Row sums = A173110: (1, 1, 3, 6, 20, 60, 230, 950, 4420, 22230,...). %F A173111 Let triangle A173108 = Q, and M = an infinite lower triangular matrix with A173110 as the rightmost diagonal and the rest zeros. Triangle A173111 = Q*M. %e A173111 First few rows of the triangle = %e A173111 1; %e A173111 1; %e A173111 2, 1; %e A173111 5, 1; %e A173111 15, 2, 3; %e A173111 52, 5, 3; %e A173111 203, 15, 6, 6; %e A173111 877, 52, 15, 6; %e A173111 4140, 203, 45, 12, 20; %e A173111 21147, 877, 156, 30, 20; %e A173111 115975, 4140, 609, 90, 40, 60; %e A173111 678570, 21147, 2631, 312, 100, 60; %e A173111 ... %e A173111 Example: row 7 = termwise products of (877, 52, 5, 1) and (1, 1, 3, 6) = %e A173111 (877, 52, 15, 6); where (877, 52, 5, 1) = row 7 of triangle A173108, and %e A173111 (1, 1, 3, 6) = the first four terms of sequence A173109. %Y A173111 A173108, A173109, A173110 %K A173111 nonn,tabl %O A173111 0,3 %A A173111 _Gary W. Adamson_, Feb 09 2010