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A231950
Number of (n+1)X(1+1) 0..1 arrays with every element equal to some horizontal, vertical, diagonal or antidiagonal neighbor, with top left element zero
8
4, 18, 64, 236, 888, 3336, 12512, 46928, 176032, 660320, 2476928, 9291200, 34852224, 130734208, 490397184, 1839529216, 6900259328, 25883567616, 97091868672, 364201376768, 1366156040192, 5124588881920, 19222848954368, 72106842214400
OFFSET
1,1
COMMENTS
Column 1 of A231957
LINKS
FORMULA
Empirical: a(n) = 4*a(n-1) -2*a(n-2) +4*a(n-3)
EXAMPLE
Some solutions for n=7
..0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..1....0..1
..0..0....0..0....1..0....0..1....0..0....0..1....0..1....1..0....1..0....0..1
..0..1....0..0....1..0....1..0....0..0....0..1....1..1....1..1....0..1....0..0
..0..1....1..0....1..0....1..0....1..0....0..0....0..1....0..1....0..1....1..0
..1..1....0..1....0..0....1..0....0..1....0..0....0..1....0..1....1..0....0..1
..0..1....1..0....0..1....0..1....0..1....1..1....1..0....1..1....0..0....0..1
..1..0....0..1....1..1....1..0....1..0....0..1....1..0....0..0....1..0....1..0
..0..1....1..1....0..0....0..0....0..0....0..1....0..1....1..1....1..0....0..0
CROSSREFS
Sequence in context: A362316 A255611 A022728 * A246134 A115112 A171074
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 15 2013
STATUS
approved