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 A143908 #2 Mar 30 2012 17:25:32 %S A143908 1,3,1,3,3,4,3,3,12,10,3,3,12,30,28,3,3,12,30,84,76,3,3,12,30,84,228, %T A143908 208,3,3,12,30,84,228,624,568,3,3,12,30,84,228,624,1704,1552 %N A143908 Eigentriangle by rows, n terms of (3 * A026150) followed by A026150(n). %C A143908 Right border = A026150: (1, 1, 4, 10, 28, 76, 208, 568,...). %C A143908 Row sums = (1, 4, 10, 28, 76,...) = INVERT transform of (1, 3, 3, 3,...). %C A143908 Sum of n-th row terms = rightmost term of next row. %F A143908 Eigentriangle by rows, n terms of (3 * A026150) followed by A026150(n). %e A143908 First few rows of the triangle = %e A143908 1; %e A143908 3, 1; %e A143908 3, 3, 4; %e A143908 3, 3, 12, 10; %e A143908 3, 3, 12, 30, 28; %e A143908 3, 3, 12, 30, 84, 76; %e A143908 3, 3, 12, 30, 84, 228, 208; %e A143908 ... %Y A143908 A026150 %K A143908 nonn,tabl %O A143908 0,2 %A A143908 _Gary W. Adamson_, Sep 06 2008