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, 2, 11, 44, 188, 752, 3056, 12224, 49088, 196352, 786176, 3144704, 12581888, 50327552, 201322496, 805289984, 3221209088, 12884836352, 51539542016, 206158168064, 824633458688, 3298533834752, 13194138484736, 52776553938944

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