A224668 Number of 6 X 6 0..n matrices with each 2 X 2 subblock idempotent.

428, 542, 668, 806, 956, 1118, 1292, 1478, 1676, 1886, 2108, 2342, 2588, 2846, 3116, 3398, 3692, 3998, 4316, 4646, 4988, 5342, 5708, 6086, 6476, 6878, 7292, 7718, 8156, 8606, 9068, 9542, 10028, 10526, 11036, 11558, 12092, 12638, 13196, 13766, 14348

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 6*n^2 + 96*n + 326.

Conjectures from Colin Barker, Sep 02 2018: (Start)

G.f.: 2*x*(214 - 371*x + 163*x^2) / (1 - x)^3.

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>3.

(End)

Example

Some solutions for n=3:
..1..0..0..0..1..0....1..1..1..1..1..0....1..0..1..0..0..3....1..0..1..0..0..1
..1..0..0..0..1..0....0..0..0..0..0..0....1..0..1..0..0..1....1..0..1..0..0..1
..1..0..0..0..1..0....1..1..1..1..1..1....0..0..1..0..0..1....1..0..1..0..0..1
..1..0..0..0..1..0....0..0..0..0..0..0....0..0..1..0..0..1....1..0..1..0..0..1
..1..0..0..0..1..0....1..1..1..1..1..1....0..0..1..0..0..1....1..0..1..0..0..1
..2..0..0..0..1..0....0..0..0..0..0..0....0..0..1..0..0..1....0..0..1..0..0..1

Crossrefs

Row 6 of A224665.

Sequence in context: A095811 A235217 A236383 * A343536 A030467 A253505

Adjacent sequences: A224665 A224666 A224667 * A224669 A224670 A224671

Keyword

nonn

Author

R. H. Hardin, Apr 14 2013

Status

approved