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A226867 Number of n X 3 (-1,0,1) arrays of determinants of 2 X 2 subblocks of some (n+1) X 4 binary array with rows and columns of the latter in lexicographically nondecreasing order. 1
7, 37, 187, 792, 2866, 9136, 26267, 69311, 170084, 392159, 856558, 1784149, 3563340, 6855064, 12751438, 23010044, 40392728, 69146369, 115673477, 189452998, 304286614, 479963424, 744456493, 1136788693, 1710732884, 2539543163 (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) = (1/2217600)*n^11 - (1/403200)*n^10 + (11/48384)*n^9 - (1/1344)*n^8 + (947/50400)*n^7 + (701/57600)*n^6 - (1447/80640)*n^5 + (7159/2688)*n^4 - (2391281/302400)*n^3 + (1074793/50400)*n^2 - (204143/9240)*n + 14 for n>1.

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

G.f.: x*(7 - 47*x + 205*x^2 - 550*x^3 + 1029*x^4 - 1353*x^5 + 1280*x^6 - 857*x^7 + 409*x^8 - 136*x^9 + 34*x^10 - 2*x^11 - x^12) / (1 - x)^12.

a(n) = 12*a(n-1) - 66*a(n-2) + 220*a(n-3) - 495*a(n-4) + 792*a(n-5) - 924*a(n-6) + 792*a(n-7) - 495*a(n-8) + 220*a(n-9) - 66*a(n-10) + 12*a(n-11) - a(n-12) for n>13.

(End)

EXAMPLE

Some solutions for n=4:

..0.-1..1....0.-1..1...-1..0..0...-1..0..0....0..0..0....0..0..0....0..0.-1

.-1..0..0...-1..0..0....0..0..0....0..0..0....0..0.-1....0..0.-1....0..0..0

..0..1.-1....1..0..0....0..0.-1....0..0..0...-1..1..0....0.-1..1....0..0..1

..0..0..1....0..1.-1....0..0..1....1..0..0....1.-1.-1...-1..0..0....0.-1..0

CROSSREFS

Column 3 of A226870.

Sequence in context: A117424 A192811 A037546 * A140476 A057651 A106925

Adjacent sequences:  A226864 A226865 A226866 * A226868 A226869 A226870

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jun 20 2013

STATUS

approved

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Last modified May 23 18:45 EDT 2019. Contains 323528 sequences. (Running on oeis4.)