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
Examples
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; ...
Extensions
a(47), a(49) corrected and more terms from Georg Fischer, Jun 07 2023
Comments