A266543 - OEIS

A266543

Number of n X 4 binary arrays with rows and columns lexicographically nondecreasing and row and column sums nonincreasing.

2, 4, 6, 12, 16, 27, 36, 57, 76, 114, 149, 213, 276, 379, 485, 645, 811, 1051, 1304, 1652, 2021, 2511, 3034, 3709, 4431, 5338, 6311, 7510, 8795, 10352, 12020, 14010, 16142, 18653, 21340, 24469, 27813, 31669, 35786, 40492, 45507, 51196, 57252, 64073, 71324

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..179

FORMULA

Empirical: a(n) = a(n-1) + 2*a(n-2) - a(n-3) - a(n-4) - a(n-5) - a(n-6) + 2*a(n-8) + 2*a(n-9) - a(n-11) - a(n-12) - a(n-13) - a(n-14) + 2*a(n-15) + a(n-16) - a(n-17).

Empirical g.f.: x*(2 + 2*x - 2*x^2 - 2*x^4 - x^5 + x^6 + 5*x^7 + 4*x^8 + 3*x^9 - x^10 - 2*x^11 - 2*x^12 - x^13 + 4*x^14 + 2*x^15 - 2*x^16) / ((1 - x)^6*(1 + x)^3*(1 + x^2)*(1 + x + x^2)*(1 + x + x^2 + x^3 + x^4)). - Colin Barker, Jan 10 2019

EXAMPLE

Some solutions for n=6:

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

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

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

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

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

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

CROSSREFS

Column 4 of A266547.

Sequence in context: A007416 A293132 A098895 * A330711 A220219 A284456

Adjacent sequences: A266540 A266541 A266542 * A266544 A266545 A266546

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 31 2015

STATUS

approved