A207025 - OEIS

A207025

Number of 2 X n 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 0 1 and 1 0 1 vertically.

4, 16, 36, 81, 169, 324, 625, 1156, 2116, 3844, 6889, 12321, 21904, 38809, 68644, 121104, 213444, 375769, 660969, 1162084, 2042041, 3587236, 6300100, 11062276, 19421649, 34093921, 59845696, 105042001, 184362084, 323568144, 567868900

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OFFSET

1,1

COMMENTS

Row 2 of A207024.

LINKS

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

FORMULA

Empirical: a(n) = 2*a(n-1) + a(n-2) - a(n-3) - 4*a(n-4) + 2*a(n-5) + a(n-7) + a(n-9) - a(n-10).

Empirical g.f.: x*(4 + 8*x - 3*x^3 + 3*x^4 - 3*x^5 + x^6 - x^7 + x^8 - x^9) / ((1 - x)*(1 - 2*x + x^2 - x^3)*(1 + x - x^3)*(1 - x^2 - x^3)). - Colin Barker, Feb 17 2018

EXAMPLE

Some solutions for n=4:

1 1 1 1 1 1 1 1 1 0 0 1 0 0 1 0 0 1 0 0

0 1 0 1 1 1 1 1 0 1 0 0 0 1 0 1 0 0 1 0

CROSSREFS

Sequence in context: A166721 A085040 A030179 * A207170 A207069 A207436

Adjacent sequences: A207022 A207023 A207024 * A207026 A207027 A207028

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 14 2012

STATUS

approved