1,1

Given A132918 = matrix M, then M * any sequence as a vector replaces alternate terms with zeros; e.g. M * [1,2,3,...] = [1,0,3,0,5,...]. M * (any infinite lower triangular matrix) replaces alternate rows with zeros; e.g. M * A007318 = (1; 0,0; 1,2,1; 0,0,0,0;...).

Identity matrix with interpolated zeros, such that the diagonal of an infinite lower triangular matrix = (1, 0, 1, 0, 1,...) with the rest zeros. a(n) = 1 if n = a hexagonal number, A000384: (1, 6, 15, 28, 45, 66,...); zero otherwise.

First few rows of the triangle are:

1;

0, 0;

0, 0, 1;

0, 0, 0, 0;

0, 0, 0, 0, 1;

...

Sequence in context: A015959 A014834 A015659 this_sequence A133943 A014084 A014159

Adjacent sequences: A132915 A132916 A132917 this_sequence A132919 A132920 A132921

nonn,tabl

Gary W. Adamson (qntmpkt(AT)yahoo.com), Sep 05 2007