A128077 - OEIS

%I #6 Feb 15 2022 02:11:04

%S 1,1,4,1,2,9,1,2,3,16,1,2,3,4,25,1,2,3,4,5,36,1,2,3,4,5,6,49,1,2,3,4,

%T 5,6,7,64

%N A128064 * A002260.

%C Row sums = the pentagonal numbers, A000326: 1, 5, 12, 22, 35, 51, ...

%F A128064 * A002260 as infinite lower triangular matrices. Triangle read by rows, a(1) = 1; n-th row = first (n-1) terms of (1, 2, 3, ...) followed by n^2.

%e First few rows of the triangle:

%e   1;

%e   1, 4;

%e   1, 2, 9;

%e   1, 2, 3, 16;

%e   1, 2, 3,  4, 25;

%e   ...

%Y Cf. A128064, A002260, A000326, A128078.

%K nonn,tabl

%O 1,3

%A _Gary W. Adamson_, Feb 14 2007