A128489 Triangle read by rows: A000012 * A126988 as infinite lower triangular matrices.

1, 3, 1, 6, 1, 1, 10, 3, 1, 1, 15, 3, 1, 1, 1, 21, 6, 3, 1, 1, 1, 28, 6, 3, 1, 1, 1, 1, 36, 10, 3, 3, 1, 1, 1, 1, 45, 10, 6, 3, 1, 1, 1, 1, 1, 55, 15, 6, 3, 3, 1, 1, 1, 1, 1, 66, 15, 6, 3, 3, 1, 1, 1, 1, 1, 1, 78, 21, 10, 6, 3, 3, 1, 1, 1, 1, 1, 1, 91, 21, 10, 6, 3, 3, 1, 1, 1, 1, 1, 1, 1

Offset: 1

Author

Gary W. Adamson, Mar 04 2007

Keywords

• nonn
• tabl

Comments

Row sums = A024916: (1, 4, 8, 15, 21, 33, ...).

Examples

			First few rows of the triangle:
   1;
   3,  1;
   6,  1, 1;
  10,  3, 1, 1;
  15,  3, 1, 1, 1;
  21,  6, 3, 1, 1, 1;
  28,  6, 3, 1, 1, 1, 1;
  36, 10, 3, 3, 1, 1, 1, 1;
  45, 10, 6, 3, 1, 1, 1, 1, 1;
  ...
		

Crossrefs

Cf. A000012, A000217, A024916, A126988.

Formula

By columns, k=1,2,3,...; k repeated terms of the triangular series, (1, 3, 6, 10, ...) in the k-th column.

Extensions

a(11) = 1 inserted and more terms from Georg Fischer, May 29 2023