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A181279 Number of 3 X n binary matrices M with rows in strictly increasing order and rows of M*Mtranspose (mod 2) in strictly decreasing order. 1
0, 0, 9, 79, 766, 6060, 49928, 395024, 3170784, 25244608, 201926272, 1612664064, 12897654272, 103124642816, 824888150016, 6597998055424, 52781434593280, 422230539485184, 3377790630133760, 27021938497224704, 216174442832068608 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Row 3 of A181274.

LINKS

R. H. Hardin, Table of n, a(n) for n=1..144

FORMULA

Empirical (for n>=3): 3*2^(3*n-7) + (18*n - 105 - 17*(-1)^n)*4^(n-4)/3 - (6*n - 19 - 3*(-1)^n)*2^(n-5)/3. - Vaclav Kotesovec, Nov 27 2012

Conjectures from Colin Barker, Mar 27 2018: (Start)

G.f.: x^3*(9 - 47*x - 16*x^2 + 124*x^3 + 224*x^4 - 320*x^5 + 512*x^6) / ((1 - 2*x)^2*(1 + 2*x)*(1 - 4*x)^2*(1 + 4*x)*(1 - 8*x)).

a(n) = 14*a(n-1) - 36*a(n-2) - 216*a(n-3) + 1056*a(n-4) - 384*a(n-5) - 3584*a(n-6) + 4096*a(n-7) for n>9.

(End)

EXAMPLE

M and M*Mtranspose (mod 2) for 3 X 3:

..0..1..0......1..1..0

..0..1..1......1..0..0

..1..0..0......0..0..1

CROSSREFS

Cf. A181274.

Sequence in context: A190979 A254598 A083411 * A173808 A293723 A255807

Adjacent sequences:  A181276 A181277 A181278 * A181280 A181281 A181282

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 10 2010

STATUS

approved

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Last modified August 14 01:48 EDT 2020. Contains 336474 sequences. (Running on oeis4.)