A225977 Number of n X 3 binary arrays whose sum with another n X 3 binary array containing no more than two 1s has rows and columns in lexicographically nondecreasing order.

8, 48, 252, 1178, 4722, 16361, 49811, 135672, 336189, 768900, 1642668, 3310404, 6343682, 11635425, 20537903, 35044430, 58024377, 93522432, 147134436, 226473606, 341742522, 506427905, 738136947, 1059595772, 1499832509

Offset: 1

Author

R. H. Hardin, May 22 2013

Keywords

• nonn

Examples

			Some solutions for n=3:
..0..0..1....0..0..0....0..0..0....0..0..1....0..0..1....0..1..1....0..1..1
..1..0..0....0..1..0....1..1..1....1..0..1....0..1..0....0..1..0....0..0..1
..1..1..1....0..1..1....0..1..0....0..0..1....0..0..1....0..1..1....1..0..0
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..101

Crossrefs

Column 3 of A225982.

Formula

Empirical: a(n) = (1/4320)*n^9 + (23/6720)*n^8 + (5/336)*n^7 - (1/288)*n^6 + (659/1440)*n^5 + (443/2880)*n^4 + (80/27)*n^3 - (6203/1008)*n^2 + (2459/140)*n - 6 for n>1.

Conjectures from Colin Barker, Sep 05 2018: (Start)

G.f.: x*(8 - 32*x + 132*x^2 - 142*x^3 + 202*x^4 - 25*x^5 - 165*x^6 + 163*x^7 - 72*x^8 + 16*x^9 - x^10) / (1 - x)^10.

a(n) = 10*a(n-1) - 45*a(n-2) + 120*a(n-3) - 210*a(n-4) + 252*a(n-5) - 210*a(n-6) + 120*a(n-7) - 45*a(n-8) + 10*a(n-9) - a(n-10) for n>11.

(End)