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A262326 Number of (n+1) X (2+1) 0..1 arrays with each row and column divisible by 3, read as a binary number with top and left being the most significant bits. 2
3, 5, 15, 33, 99, 261, 783, 2241, 6723, 19845, 59535, 177633, 532899, 1595781, 4787343, 14353281, 43059843, 129153285, 387459855, 1162300833, 3486902499, 10460471301, 31381413903, 94143533121, 282430599363, 847289672325 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 2 of A262332.

LINKS

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

FORMULA

Empirical: a(n) = 3*a(n-1) + 3*a(n-2) - 9*a(n-3).

Conjectures from Colin Barker, Mar 20 2018: (Start)

G.f.: x*(3 - 4*x - 9*x^2) / ((1 - 3*x)*(1 - 3*x^2)).

a(n) = 2*3^(n/2-1) + 3^(n-1) for n even.

a(n) = 2*3^((n-3)/2+1) + 3^(n-1) for n odd.

(End)

EXAMPLE

Some solutions for n=4:

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

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

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

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

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

CROSSREFS

Cf. A262332.

Sequence in context: A182143 A193649 A186341 * A148499 A148500 A148501

Adjacent sequences:  A262323 A262324 A262325 * A262327 A262328 A262329

KEYWORD

nonn

AUTHOR

R. H. Hardin, Sep 18 2015

STATUS

approved

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Last modified July 11 18:19 EDT 2020. Contains 335652 sequences. (Running on oeis4.)