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A204391
Number of (n+2) X 3 0..1 arrays with no 3 X 3 subblock having three equal diagonal elements or three equal antidiagonal elements, and new values 0..1 introduced in row major order.
1
144, 648, 2952, 13448, 61336, 279752, 1276088, 5820872, 26552184, 121119048, 552490872, 2520216008, 11496098296, 52440058952, 239208098168, 1091160371912, 4977385663224, 22704607570248, 103568266524792, 472432117479368
OFFSET
1,1
COMMENTS
Column 1 of A204398.
LINKS
FORMULA
Empirical: a(n) = 5*a(n-1) - 10*a(n-3) + 4*a(n-4).
Empirical g.f.: 8*x*(18 - 9*x - 36*x^2 + 16*x^3) / ((1 - 5*x + 2*x^2)*(1 - 2*x^2)). - Colin Barker, Jun 07 2018
EXAMPLE
Some solutions for n=3:
..0..1..0....0..1..0....0..1..0....0..0..1....0..0..0....0..1..0....0..1..1
..0..1..1....0..1..0....0..0..1....1..0..0....1..1..1....1..0..1....0..1..1
..0..1..1....0..1..1....1..1..1....1..1..1....0..1..1....1..0..1....0..0..1
..0..1..1....1..1..0....0..1..0....0..1..0....0..1..0....0..1..1....0..0..1
..0..1..1....0..0..1....0..0..0....0..1..0....0..1..1....0..0..0....0..0..1
CROSSREFS
Cf. A204398.
Sequence in context: A180413 A137885 A204398 * A233903 A233897 A250428
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 15 2012
STATUS
approved