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

1,2

Comments

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

Links

Table of n, a(n) for n=1..91.

Formula

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

Example

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.

Sequence in context: A099512 A127096 A130541 * A034839 A089732 A158905

Adjacent sequences: A128486 A128487 A128488 * A128490 A128491 A128492

Keyword

nonn,tabl

Author

Gary W. Adamson, Mar 04 2007

Extensions

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

Status

approved