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A225894 Number of n X 2 binary arrays whose sum with another n X 2 binary array containing no more than a single 1 has rows and columns in lexicographically nondecreasing order. 1
4, 12, 33, 78, 162, 304, 527, 858, 1328, 1972, 2829, 3942, 5358, 7128, 9307, 11954, 15132, 18908, 23353, 28542, 34554, 41472, 49383, 58378, 68552, 80004, 92837, 107158, 123078, 140712, 160179, 181602, 205108, 230828, 258897, 289454, 322642 (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) = (1/6)*n^4 + (1/6)*n^3 + (4/3)*n^2 + (1/3)*n + 2.

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

G.f.: x*(4 - 8*x + 13*x^2 - 7*x^3 + 2*x^4) / (1 - x)^5.

a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>5.

(End)

EXAMPLE

Some solutions for n=3:

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

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

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

CROSSREFS

Column 2 of A225900.

Sequence in context: A265212 A295500 A168078 * A318637 A227554 A305778

Adjacent sequences:  A225891 A225892 A225893 * A225895 A225896 A225897

KEYWORD

nonn

AUTHOR

R. H. Hardin, May 20 2013

STATUS

approved

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Last modified August 2 15:26 EDT 2021. Contains 346428 sequences. (Running on oeis4.)