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A225895 Number of n X 3 binary arrays whose sum with another n X 3 binary array containing no more than a single 1 has rows and columns in lexicographically nondecreasing order. 1
7, 33, 145, 545, 1770, 5052, 12910, 30055, 64701, 130387, 248427, 451117, 785840, 1320222, 2148504, 3399307, 5244979, 7912725, 11697733, 16978521, 24234742, 34067696, 47223810, 64621359, 87380713, 116858407, 154685343, 202809445 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = (1/3360)*n^8 + (3/560)*n^7 + (5/144)*n^6 + (7/120)*n^5 + (761/1440)*n^4 + (81/80)*n^3 + (122/63)*n^2 + (89/210)*n + 3.

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

G.f.: x*(7 - 30*x + 100*x^2 - 160*x^3 + 195*x^4 - 162*x^5 + 82*x^6 - 23*x^7 + 3*x^8) / (1 - x)^9.

a(n) = 9*a(n-1) - 36*a(n-2) + 84*a(n-3) - 126*a(n-4) + 126*a(n-5) - 84*a(n-6) + 36*a(n-7) - 9*a(n-8) + a(n-9) for n>9.

(End)

EXAMPLE

Some solutions for n=3:

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

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

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

CROSSREFS

Column 3 of A225900.

Sequence in context: A034577 A141291 A278027 * A089106 A211829 A227555

Adjacent sequences:  A225892 A225893 A225894 * A225896 A225897 A225898

KEYWORD

nonn

AUTHOR

R. H. Hardin, May 20 2013

STATUS

approved

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Last modified August 4 21:32 EDT 2021. Contains 346455 sequences. (Running on oeis4.)