A221313 - OEIS

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A221313

Square root of number of nX4 arrays of occupancy after each element moves to some horizontal or vertical neighbor, with every occupancy equal to zero or two

1, 4, 9, 23, 57, 142, 353, 878, 2183, 5428, 13496, 33556, 83432, 207441, 515770, 1282382, 3188443

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

OFFSET

1,2

COMMENTS

Column 4 of A221314

LINKS

Table of n, a(n) for n=1..17.

FORMULA

Empirical: a(n) = 2*a(n-1) + 2*a(n-2) - a(n-3) - 2*a(n-4) - a(n-5). - Vaclav Kotesovec, May 23 2013

EXAMPLE

Some solutions for n=3