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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 1 of A231957

LINKS

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

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: A083321 A255611 A022728 * A246134 A115112 A171074

Adjacent sequences:  A231947 A231948 A231949 * A231951 A231952 A231953

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 15 2013

STATUS

approved

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Last modified October 21 05:02 EDT 2019. Contains 328291 sequences. (Running on oeis4.)