A131226 Triangle read by rows: 3*A002260 - 2*A128174 as infinite lower triangular matrices.

1, 3, 4, 1, 6, 7, 3, 4, 9, 10, 1, 6, 7, 12, 13, 3, 4, 9, 10, 15, 16, 1, 6, 7, 12, 13, 18, 19, 3, 4, 9, 10, 15, 16, 21, 22, 1, 6, 7, 12, 13, 18, 19, 24, 25, 3, 4, 9, 10, 15, 16, 21, 22, 27, 28, 1, 6, 7, 12, 13, 18, 19, 24, 25, 30, 31, 3, 4, 9, 10, 15, 16, 21, 22, 27, 28, 33, 34

Offset

1,2

Comments

Row sums = A095894: (1, 7, 14, 26, 39, 57, ...).

A131225 = 2*A002260 - A128174.

Links

Table of n, a(n) for n=1..78.

Example

First few rows of the triangle:
  1;
  3, 4;
  1, 6, 7;
  3, 4, 9, 10;
  1, 6, 7, 12, 13;
  3, 4, 9, 10, 15, 16;
  1, 6, 7, 12, 13, 18, 19;
  ...

Crossrefs

Cf. A002260, A095894, A128174, A131225.

Sequence in context: A254525 A132179 A089029 * A286577 A175323 A359268

Adjacent sequences: A131223 A131224 A131225 * A131227 A131228 A131229

Keyword

nonn,tabl

Author

Gary W. Adamson, Jun 20 2007

Extensions

a(47), a(49) corrected and more terms from Georg Fischer, Jun 07 2023

Status

approved