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A202796
Number of n X 2 binary arrays with every one adjacent to another one horizontally or vertically.
4
2, 10, 36, 126, 454, 1632, 5854, 21010, 75412, 270662, 971438, 3486624, 12513958, 44914250, 161203204, 578579694, 2076599286, 7453190368, 26750489166, 96011055010, 344596415668, 1236802258678, 4439047411742, 15932330156576
OFFSET
1,1
COMMENTS
Column 2 of A202802.
LINKS
FORMULA
Empirical: a(n) = 3*a(n-1) + a(n-2) + 4*a(n-3).
Empirical g.f.: 2*x*(1 + 2*x + 2*x^2) / (1 - 3*x - x^2 - 4*x^3). - Colin Barker, Feb 20 2018
EXAMPLE
Some solutions for n=5:
..0..1....0..0....0..1....1..0....0..0....1..0....1..1....0..1....0..1....1..0
..0..1....1..0....1..1....1..0....0..0....1..0....1..1....1..1....1..1....1..1
..1..1....1..1....1..1....1..1....0..1....0..0....1..0....0..0....1..0....0..1
..1..1....0..1....1..0....1..0....0..1....0..1....0..1....1..0....0..0....1..0
..1..0....1..1....1..0....1..0....0..0....0..1....1..1....1..1....0..0....1..0
CROSSREFS
Cf. A202802.
Sequence in context: A266942 A265844 A192858 * A335559 A001582 A357035
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 24 2011
STATUS
approved