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 A152227 #7 Jun 02 2025 01:13:41 %S A152227 1,2,1,2,2,3,4,2,6,7,8,4,6,14,19,18,8,12,14,38,51,42,18,24,28,38,102, %T A152227 141,102,42,54,56,76,102,282,393254,102,126,126,152,204,282,786,1107, %U A152227 646,254,306,2944,342,408,564,786,2214,3139 %N A152227 Eigentriangle, row sums = A002426. %C A152227 Row sums = A002426 starting with offset 1: (1, 3, 7, 19, 51, 141, 393,...). %C A152227 Right border = A002426, left border = A007971 %C A152227 Sum of n-th row terms = rightmost term of next row. %F A152227 Triangle read by rows, M*Q. M = an infinite lower triangular matrix with A007971 in every column: (1, 2, 2, 4, 8, 18, 42,...); and Q = a matrix with A002426 as the main diagonal and the rest zeros. %e A152227 First few rows of the triangle = %e A152227 1; %e A152227 2, 1; %e A152227 2, 2, 3; %e A152227 4, 2, 6, 7; %e A152227 8, 4, 6, 14, 19; %e A152227 18, 8, 12, 14, 38, 51; %e A152227 42, 18, 24, 28, 38, 102, 141; %e A152227 102, 42, 54, 56, 76, 102, 282, 393; %e A152227 254, 102, 126, 126, 152, 204, 282, 786, 1107; %e A152227 646, 254, 306, 394, 342, 408, 564, 786, 2214, 3139; %e A152227 ... %e A152227 Row 3 = (4, 2, 6, 7) = termwise products of (4, 2, 2, 1) and (1, 1, 3, 7) %K A152227 nonn,tabl %O A152227 1,2 %A A152227 _Gary W. Adamson_, Nov 29 2008