A224664 Number of n X n 0..7 matrices with each 2X2 subblock idempotent

8, 32, 200, 318, 700, 1292, 2476, 4570, 8406, 15256, 27498, 49198, 87530, 154940, 273084, 479466, 838944, 1463400, 2545472, 4416198, 7643450, 13199732, 22747870, 39126778, 67176430

Offset

1,1

Comments

Column 7 of A224665

Links

Table of n, a(n) for n=1..25.

Formula

Empirical: a(n) = 6*a(n-1) -12*a(n-2) +5*a(n-3) +12*a(n-4) -12*a(n-5) -3*a(n-6) +6*a(n-7) -a(n-9) for n>10

Empirical g.f.: 8*x -2*x^2 *(-16 -4*x +249*x^2 -516*x^3 +238*x^4 +241*x^5 -199*x^6 -31*x^7 +35*x^8) /(x-1)^3 /(x^2+x-1)^3 . - R. J. Mathar, Nov 09 2018

Example

Some solutions for n=3
..1..0..0....1..0..4....1..1..6....1..1..5....1..0..0....1..0..6....1..1..2
..1..0..0....0..0..1....0..0..0....0..0..0....1..0..1....1..0..1....0..0..0
..4..0..0....0..0..1....0..1..1....0..0..1....1..0..1....2..0..1....7..1..1

Crossrefs

Sequence in context: A086348 A129798 A129792 * A222692 A268143 A093759

Adjacent sequences: A224661 A224662 A224663 * A224665 A224666 A224667

Keyword

nonn

Author

R. H. Hardin Apr 14 2013

Status

approved