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
Keywords
Examples
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
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
Comments