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 A152229 #7 Jun 02 2025 01:13:48 %S A152229 1,1,1,3,1,2,9,3,2,6,29,9,6,6,20,97,29,18,18,20,70,333,97,58,54,60,70, %T A152229 252,1165,333,194,174,180,210,252,924,4135,1165,666,582,580,630,756, %U A152229 924,3432,14845,4135,2330,1998,1940,2030,2268,2772,3432,12870 %N A152229 Eigentriangle, row sums = A000984. %C A152229 Row sums = A000984: (1, 2, 6, 20, 70, 252,...), left border = A081696. %C A152229 Sum of n-th row terms = rightmost term of next row. %F A152229 Triangle read by rows, M*Q. M = an infinite lower triangular matrix with A081696: (1, 1, 3, 9, 29, 97, 333, 1165,...) in every column; and Q = a matrix with A000984 as the main diagonal (prefaced with a 1): (1, 1, 2, 6, 20, 70, 252,...) and the rest zeros. %e A152229 First few rows of the triangle = %e A152229 1; %e A152229 1, 1; %e A152229 3, 1, 2; %e A152229 9, 3, 2, 6; %e A152229 29, 9, 6, 6, 20; %e A152229 97, 29, 18, 18, 20, 70; %e A152229 333, 97, 58, 54, 60, 70, 252; %e A152229 1165, 333, 194, 174, 180, 210, 252, 924; %e A152229 4135, 1165, 666, 582, 580, 630, 756, 924, 3432; %e A152229 14845, 4135, 2330, 1998, 1940, 2030, 2268, 2772, 3432, 12870; %e A152229 ... %e A152229 Row 3 = (9, 3, 2, 6) = termwise products of (9, 3, 1, 1) and (1, 1, 2, 6). %Y A152229 Cf. A000984, A081696. %K A152229 nonn,tabl %O A152229 0,4 %A A152229 _Gary W. Adamson_, Nov 29 2008