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A296111
Number of nX4 0..1 arrays with each 1 adjacent to 3 or 4 king-move neighboring 1s.
1
1, 4, 9, 16, 64, 185, 528, 2109, 7336, 25548, 96284, 350352, 1275030, 4720164, 17327263, 63606177, 234363052, 861828278, 3169215181, 11663750978, 42906823150, 157839351044, 580741120133, 2136506975344, 7860072868753
OFFSET
1,2
COMMENTS
Column 4 of A296115.
FORMULA
Empirical: a(n) = a(n-1) +7*a(n-2) +21*a(n-3) -6*a(n-4) -85*a(n-5) -132*a(n-6) -69*a(n-7) +142*a(n-8) +445*a(n-9) +490*a(n-10) +185*a(n-11) -220*a(n-12) -588*a(n-13) -549*a(n-14) +23*a(n-15) +683*a(n-16) +168*a(n-17) -655*a(n-18) -594*a(n-19) -256*a(n-20) +387*a(n-21) +385*a(n-22) -14*a(n-23) -86*a(n-24) -20*a(n-25) +6*a(n-26) +2*a(n-27).
Empirical formula verified by Robert Israel, Dec 05 2017 (see link).
EXAMPLE
Some solutions for n=7
..0..0..0..0. .0..0..0..0. .1..1..0..0. .0..0..0..0. .1..1..0..0
..0..1..0..0. .0..0..0..0. .1..1..0..0. .1..1..0..0. .1..1..0..0
..1..1..1..0. .0..1..1..0. .0..0..0..0. .1..1..0..0. .0..0..0..0
..0..1..0..0. .0..1..1..0. .0..0..0..0. .0..0..0..0. .0..0..0..0
..0..0..0..0. .1..0..0..0. .0..0..0..0. .0..0..0..0. .0..0..1..0
..1..1..0..0. .1..1..0..0. .0..0..1..1. .0..0..0..0. .0..1..1..1
..1..1..0..0. .1..1..0..0. .0..0..1..1. .0..0..0..0. .0..0..1..0
CROSSREFS
Cf. A296115.
Sequence in context: A073723 A161493 A030075 * A038784 A038239 A352919
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 04 2017
STATUS
approved