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R. H. Hardin, <a href="/A295526/b295526.txt">Table of n, a(n) for n = 1..210</a>

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Number of nX3 0..1 arrays with each 1 horizontally or vertically adjacent to 1, 2 or 4 1s.

4, 29, 147, 774, 4080, 21489, 113466, 598374, 3155426, 16642084, 87770692, 462903372, 2441353234, 12875695490, 67906455891, 358138834199, 1888825058236, 9961667898631, 52537860596653, 277084804179135, 1461345928848848

1,1

Column 3 of A295531.

Empirical: a(n) = 4*a(n-1) +3*a(n-2) +15*a(n-3) +17*a(n-4) +40*a(n-5) -6*a(n-6) -12*a(n-7) +45*a(n-8) -21*a(n-9) -66*a(n-10) +7*a(n-11) +6*a(n-12) -6*a(n-13) +6*a(n-14) +a(n-15) -3*a(n-16) +a(n-18)

Some solutions for n=5

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

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

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

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

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

Cf. A295531.

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R. H. Hardin, Nov 23 2017

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