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 A133981 #9 Jun 07 2023 04:40:46 %S A133981 1,4,3,5,6,5,6,7,8,7,7,8,9,10,9,8,9,10,11,12,11,9,10,11,12,13,14,13, %T A133981 10,11,12,13,14,15,16,15,11,12,13,14,15,16,17,18,17,12,13,14,15,16,17, %U A133981 18,19,20,19,13,14,15,16,17,18,19,20,21,22,21,14,15,16,17,18,19,20,21,22,23,24,23 %N A133981 Triangle read by rows: A000012 * A127701 + A127701 * A000012 - A000012 as infinite lower triangular matrices. %C A133981 Row sums = A133694: (1, 7, 16, 28, 43, 61, ...). %e A133981 First few rows of the triangle: %e A133981 1; %e A133981 4, 3; %e A133981 5, 6, 5; %e A133981 6, 7, 8, 7; %e A133981 7, 8, 9, 10, 9; %e A133981 8, 9, 10, 11, 12, 11; %e A133981 9, 10, 11, 12, 13, 14, 13; %e A133981 10, 11, 12, 13, 14, 15, 16, 15; %e A133981 11, 12, 13, 14, 15, 16, 17, 18, 17; %e A133981 ... %Y A133981 Cf. A127701, A133694. %K A133981 nonn,tabl %O A133981 1,2 %A A133981 _Gary W. Adamson_, Sep 30 2007 %E A133981 a(26) = 13 corrected and more terms from _Georg Fischer_, Jun 07 2023