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A181270 Number of 2 X n binary matrices M with rows in strictly increasing order and rows of M*Mtranspose (mod 2) in strictly increasing order. 1
1, 2, 11, 44, 188, 752, 3056, 12224, 49088, 196352, 786176, 3144704, 12581888, 50327552, 201322496, 805289984, 3221209088, 12884836352, 51539542016, 206158168064, 824633458688, 3298533834752, 13194138484736, 52776553938944 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row 2 of A181266.

LINKS

R. H. Hardin, Table of n, a(n) for n=1..200

FORMULA

Empirical (for n>=2): 3*4^(n-2) - (3+(-1)^n)*2^(n-4). - Vaclav Kotesovec, Nov 27 2012

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

G.f.: x*(1 - 2*x - x^2 + 8*x^3) / ((1 - 2*x)*(1 + 2*x)*(1 - 4*x)).

a(n) = 4*a(n-1) + 4*a(n-2) - 16*a(n-3) for n>4.

(End)

EXAMPLE

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

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

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

CROSSREFS

Cf. A181266.

Sequence in context: A181369 A037744 A037625 * A110679 A127109 A054208

Adjacent sequences:  A181267 A181268 A181269 * A181271 A181272 A181273

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 10 2010

STATUS

approved

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Last modified September 22 07:34 EDT 2020. Contains 337289 sequences. (Running on oeis4.)