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A226866 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. 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = (1/40)*n^5 + (7/8)*n^3 + (21/10)*n + 1.

Conjectures from Colin Barker, Sep 06 2018: (Start)

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)

EXAMPLE

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

CROSSREFS

Column 2 of A226870.

Sequence in context: A279111 A299111 A324250 * A048474 A054761 A244197

Adjacent sequences:  A226863 A226864 A226865 * A226867 A226868 A226869

KEYWORD

nonn

AUTHOR

R. H. Hardin Jun 20 2013

STATUS

approved

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Last modified April 18 06:48 EDT 2019. Contains 322209 sequences. (Running on oeis4.)