A168508 Triangle read by rows: A101688 * A051731.

1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 3, 1, 1, 1, 1, 3, 2, 1, 1, 1, 1, 4, 2, 1, 1, 1, 1, 1, 4, 2, 1, 1, 1, 1, 1, 1, 5, 2, 2, 1, 1, 1, 1, 1, 1, 5, 3, 2, 1, 1, 1, 1, 1, 1, 1, 6, 3, 2, 1, 1, 1, 1, 1, 1, 1, 1, 6, 3, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 7, 3, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 7, 4, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1

Offset

1,4

Comments

More precisely, form the product of the lower triangular matrix T defined in A101688 and the lower triangular matrix T defined in A051731. - N. J. A. Sloane, Dec 05 2020

Row sums = A060831: (1, 2, 4, 5, 7, 9, 11, 12, 15,...).

A168509 = A051731 * A101688

Links

Table of n, a(n) for n=1..105.

Example

First few rows of the triangle =
1;
1, 1;
2, 1, 1;
2, 1, 1, 1;
3, 1, 1, 1, 1;
3, 2, 1, 1, 1, 1;
4, 2, 1, 1, 1, 1, 1;
4, 2, 1, 1, 1, 1, 1, 1;
5, 2, 2, 1, 1, 1, 1, 1, 1;
5, 3, 2, 1, 1, 1, 1, 1, 1, 1;
6, 3, 2, 1, 1, 1, 1, 1, 1, 1, 1;
6, 3, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1;
7, 3, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1;
7, 4, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1;
8, 4, 3, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1;
8, 4, 3, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1;
9, 4, 3, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1;
...

Crossrefs

Cf. A051731, A060831, A101688, A168509.

Sequence in context: A327522 A034003 A306722 * A177994 A179285 A079211

Adjacent sequences: A168505 A168506 A168507 * A168509 A168510 A168511

Keyword

nonn,tabl

Author

Gary W. Adamson, Nov 27 2009

Extensions

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

Status

approved