1,3

Row sums = A157020: (1, 3, 4, 9, 6, 22, 8,...)

Triangle read by rows, A156348 * A127648. A127648 = an infinite lower triangular matrix with (1, 2, 3,...) as the main diagonal and the rest zeros.

First few rows of the triangle =

1;

1, 2;

1, 0, 3;

1, 4, 0, 4;

1, 0, 0, 0, 5;

1, 6, 9, 0, 0, 6;

1, 0, 0, 0, 0, 0, 7;

1, 8, 0, 16, 0, 0, 0, 8;

1, 0, 18, 0, 0, 0, 0, 0, 9;

1, 10, 0, 0, 25, 0, 0, 0, 0, 10;

1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 11;

1, 12, 30, 40, 0, 36, 0, 0, 0, 0, 0, 12;

1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 13;

1, 14, 0, 0, 0, 0, 49, 0, 0, 0, 0, 0, 0, 14;

...

Row 4 = (1, 4, 0, 4) = termwise products of (1, 2, 0, 1) and (1, 2, 3, 4)

where (1, 2, 0, 1) = row 4 of triangle A156348.

Cf. A156348, A126648, A156020

Sequence in context: A146540 A162922 A102057 this_sequence A131358 A117901 A074984

Adjacent sequences: A157494 A157495 A157496 this_sequence A157498 A157499 A157500

nonn,tabl

Gary W. Adamson & Mats Granvik (qntmpkt(AT)yahoo.com), Mar 01 2009