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A302516 Number of 3Xn 0..1 arrays with every element equal to 0, 1, 4 or 5 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. 1
4, 4, 11, 15, 21, 52, 118, 220, 408, 852, 1764, 3460, 6796, 13732, 27708, 55140, 109788, 220132, 441244, 881380, 1760796, 3523812, 7051548, 14098660, 28189468, 56387812, 112791324, 225564900, 451098396, 902232292, 1804527388, 3608983780 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 3 of A302515.

LINKS

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

FORMULA

Empirical: a(n) = a(n-1) +2*a(n-3) +4*a(n-4) for n>7

EXAMPLE

Some solutions for n=5

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

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

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

CROSSREFS

Cf. A302515.

Sequence in context: A265206 A327684 A231064 * A254205 A048223 A214112

Adjacent sequences:  A302513 A302514 A302515 * A302517 A302518 A302519

KEYWORD

nonn

AUTHOR

R. H. Hardin, Apr 09 2018

STATUS

approved

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Last modified July 9 16:50 EDT 2020. Contains 335545 sequences. (Running on oeis4.)