A224672 Number of (n+1) X 5 0..2 matrices with each 2 X 2 subblock idempotent.
70, 123, 170, 260, 381, 573, 864, 1322, 2043, 3191, 5026, 7972, 12713, 20357, 32696, 52630, 84851, 136951, 221214, 357516, 578017, 934753, 1511920, 2445750, 3956671, 6401343, 10356854, 16756952, 27112473, 43868001, 70978956, 114845342
Offset: 1
Keywords
Examples
Some solutions for n=3: ..0..0..1..0..0....1..1..0..1..0....0..1..0..0..0....1..0..0..0..1 ..0..0..1..0..0....0..0..0..1..0....0..1..0..0..0....1..0..0..0..1 ..0..0..1..0..1....0..0..0..1..0....0..1..0..0..0....0..0..0..0..1 ..0..0..1..0..1....0..0..0..1..0....0..1..0..0..1....0..0..0..0..1
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Formula
Empirical: a(n) = 4*a(n-1) -5*a(n-2) +a(n-3) +2*a(n-4) -a(n-5) for n>6.
Empirical g.f.: x*(70 - 157*x + 28*x^2 + 125*x^3 - 72*x^4 + 3*x^5) / ((1 - x)^3*(1 - x - x^2)). - Colin Barker, Feb 17 2018
Comments