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 A135871 #10 Mar 30 2024 23:09:17 %S A135871 1,0,3,-1,0,9,0,-6,0,27,1,0,-27,0,81,0,9,0,-108,0,243,-1,0,54,0,-405, %T A135871 0,729,0,-12,0,270,0,-1458,0,2187 %N A135871 Triangle by columns: A013610 signed and interleaved with zeros. %C A135871 Row sums = even-indexed Fibonacci numbers, A001906: (1, 3, 8, 21, 55, ...) such that the sum of n-th row terms = F(2n). Example: sum of nonzero terms of row 4 = (-6 + 27) = 21 = F(8). %F A135871 The triangle starts with A013610, then by columns sign (+, -, +, ...) and interleave with zeros. %e A135871 First few rows of the triangle: %e A135871 1; %e A135871 0, 3; %e A135871 -1, 0, 9; %e A135871 0, -6, 0, 27; %e A135871 1, 0, -27, 0, 81; %e A135871 0, 9, 0, -108, 0, 243; %e A135871 -1, 0, 54, 0, -405, 0, 729; %e A135871 ... %Y A135871 Cf. A013610, A001906. %K A135871 tabl,sign %O A135871 1,3 %A A135871 _Gary W. Adamson_, Dec 02 2007