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R. H. Hardin, <a href="/A296630/b296630.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, vertically or antidiagonally adjacent to 0, 2 or 4 neighboring 1s.

5, 19, 71, 260, 966, 3581, 13275, 49209, 182422, 676247, 2506882, 9293135, 34450119, 127708318, 473421137, 1754995884, 6505857719, 24117540693, 89404932324, 331428565852, 1228622307611, 4554564483230, 16883998852534, 62589830114818

1,1

Column 3 of A296635.

Empirical: a(n) = 2*a(n-1) +4*a(n-2) +6*a(n-3) +8*a(n-4) +6*a(n-5) +3*a(n-6) -2*a(n-7) -6*a(n-8) -8*a(n-9) -7*a(n-10) -4*a(n-11) -a(n-12)

Some solutions for n=7

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

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

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

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

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

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

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

Cf. A296635.

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R. H. Hardin, Dec 17 2017

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