A124731 - OEIS

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A124731

Triangle, row sums = powers of 3, companion to A124730.

1, 2, 1, 4, 3, 2, 8, 7, 10, 2, 16, 15, 34, 12, 4, 32, 31, 98, 46, 32, 4, 64, 63, 258, 144, 156, 36, 8, 128, 127, 642, 402, 600, 192, 88, 8, 256, 255, 1538, 1044, 2004, 792, 560, 96, 16

(list; table; graph; refs; listen; history; text; internal format)

OFFSET

0,2

COMMENTS

In A124730, the diagonals are switched. Row sums are powers of 3 in both triangles.

LINKS

Table of n, a(n) for n=0..44.

FORMULA

Let M = the infinite bidiagonal matrix with (2,1,2,1...) in the main diagonal and (1,2,1,2...) in the subdiagonal. Extracting finite n X n matrices of this form, we take M^n * [1,0,0,0...].

EXAMPLE

Row 2 = (4, 3, 2) since (using the 3 X 3 matrix m = [2,0,0; 1,1,0; 0,2,2]), m^2 * [1,0,0] = [4,3,2].

First few rows of the triangle are:

2, 1;

4, 3, 2;

8, 7, 10, 2;

16, 15, 34, 12, 4;

32, 31, 98, 46, 32, 4;

64, 63, 258, 144, 156, 36, 8;

...

CROSSREFS

Cf. A124730, A124732.