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A301946 Number of nX3 0..1 arrays with every element equal to 1, 2 or 3 horizontally or antidiagonally adjacent elements, with upper left element zero. 1
1, 5, 20, 83, 342, 1411, 5820, 24007, 99026, 408471, 1684896, 6950003, 28667966, 118252075, 487776260, 2012021183, 8299356842, 34233896031, 141210898600, 582478776747, 2402658213526, 9910689833651, 40880459994636, 168627213385143 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 3 of A301951.

LINKS

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

FORMULA

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

EXAMPLE

Some solutions for n=5

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

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

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

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

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

CROSSREFS

Cf. A301951.

Sequence in context: A183933 A323262 A295601 * A292760 A270322 A056884

Adjacent sequences:  A301943 A301944 A301945 * A301947 A301948 A301949

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 29 2018

STATUS

approved

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Last modified July 13 05:18 EDT 2020. Contains 335673 sequences. (Running on oeis4.)