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A230990 Number of n X 2 0..3 arrays x(i,j) with each element horizontally, vertically or antidiagonally next to at least one element with value (x(i,j)+1) mod 4 and at least one element with value (x(i,j)-1) mod 4, and upper left element zero. 1
0, 2, 2, 16, 66, 396, 2172, 12094, 66948, 370750, 2053660, 11374596, 63004974, 348980292, 1932997662, 10706810092, 59304740676, 328487288382, 1819482043764, 10078060648494, 55822099185980, 309197063033572, 1712633978183438 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
Empirical: a(n) = 7*a(n-1) - 5*a(n-2) - 25*a(n-3) + 47*a(n-4) - 4*a(n-5) - 100*a(n-6) + 104*a(n-7) - 36*a(n-8) + 4*a(n-9).
Empirical g.f.: 2*x^2*(1 - 6*x + 6*x^2 + 7*x^3 - 15*x^4 + 22*x^5 - 12*x^6 + 2*x^7) / (1 - 7*x + 5*x^2 + 25*x^3 - 47*x^4 + 4*x^5 + 100*x^6 - 104*x^7 + 36*x^8 - 4*x^9). - Colin Barker, Sep 25 2018
EXAMPLE
All solutions for n=3:
..0..1....0..3
..3..2....1..2
..0..1....0..3
CROSSREFS
Column 2 of A230994.
Sequence in context: A001119 A216387 A062282 * A217977 A368467 A012319
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 02 2013
STATUS
approved

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Last modified March 3 12:51 EST 2024. Contains 370512 sequences. (Running on oeis4.)