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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. 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

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)

EXAMPLE

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

CROSSREFS

Column 3 of A225982.

Sequence in context: A069021 A079763 A079785 * A305782 A292536 A242668

Adjacent sequences:  A225974 A225975 A225976 * A225978 A225979 A225980

KEYWORD

nonn

AUTHOR

R. H. Hardin, May 22 2013

STATUS

approved

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Last modified January 18 19:46 EST 2020. Contains 331030 sequences. (Running on oeis4.)