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A226866
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Number of n X 2 (-1,0,1) arrays of determinants of 2 X 2 subblocks of some (n+1) X 3 binary array with rows and columns of the latter in lexicographically nondecreasing order.
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1
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4, 13, 37, 91, 199, 397, 736, 1285, 2134, 3397, 5215, 7759, 11233, 15877, 21970, 29833, 39832, 52381, 67945, 87043, 110251, 138205, 171604, 211213, 257866, 312469, 376003, 449527, 534181, 631189, 741862, 867601, 1009900, 1170349, 1350637
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = (1/40)*n^5 + (7/8)*n^3 + (21/10)*n + 1.
G.f.: x*(4 - 11*x + 19*x^2 - 16*x^3 + 8*x^4 - x^5) / (1 - x)^6.
a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>6.
(End)
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EXAMPLE
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Some solutions for n=4:
..0..0....0..0....0..0....0..0...-1..0....0..0...-1..1...-1..0....0.-1....0.-1
..0.-1....0.-1....0..0....0..0....0..0....0.-1....1.-1....1..0....0..0...-1..0
..0..0....0..1....0.-1...-1..1....1..0...-1..0....0..0....0..0....0..1....0..0
.-1..0...-1.-1...-1.-1....0..0....0..0....1..0....0..0....0..0...-1.-1....0..0
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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