A140733 - OEIS

A140733

Triangle read by rows, X^n * [1,0,0,0,...]; where X = a tridiagonal matrix with (1,1,1,...) in the main and subdiagonals and (1,2,3,...) in the subsubdiagonal.

1, 1, 1, 1, 1, 2, 3, 3, 3, 1, 3, 6, 10, 15, 15, 15, 1, 4, 10, 22, 43, 70, 105, 105, 105, 1, 5, 15, 40, 95, 201, 390, 630, 945, 945, 945, 1, 6, 21, 65, 180, 456, 1066, 2226, 4305, 6930, 10395, 10395, 10395, 1, 7, 28, 98, 308, 896, 2422, 6028, 13993, 29043, 56070, 90090

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OFFSET

1,6

COMMENTS

Rightmost terms of each row form A001147: (1, 1, 3, 15, 105, 945,...).

LINKS

Table of n, a(n) for n=1..61.

EXAMPLE

First few rows of the triangle are:

1, 1, 1;

1, 2, 3, 3, 3;

1, 3, 6, 10, 15, 15, 15;