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A222891
Number of n X 2 0..7 arrays with no element equal to another at a city block distance of exactly two, and new values 0..7 introduced in row major order.
1
2, 7, 34, 389, 7145, 179465, 5426201, 180390761, 6268113977, 222151991177, 7942488470873, 285058950003113, 10248273625735289, 368717006467136969, 13270285321513993625, 477673900318354951145, 17195359005212203140281
OFFSET
1,1
COMMENTS
Column 2 of A222894.
LINKS
FORMULA
Empirical: a(n) = 66*a(n-1) - 1353*a(n-2) + 10648*a(n-3) - 30096*a(n-4) + 20736*a(n-5) for n>7.
Empirical g.f.: x*(2 - 125*x + 2278*x^2 - 13680*x^3 + 13129*x^4 + 41380*x^5 - 15264*x^6) / ((1 - x)*(1 - 4*x)*(1 - 9*x)*(1 - 16*x)*(1 - 36*x)). - Colin Barker, Aug 16 2018
EXAMPLE
Some solutions for n=3:
..0..1....0..0....0..0....0..1....0..1....0..1....0..1....0..1....0..1....0..1
..2..3....1..2....1..1....0..1....2..1....2..3....2..3....2..3....2..1....2..3
..2..3....3..3....2..2....2..3....2..3....1..3....4..5....1..0....3..4....4..0
CROSSREFS
Cf. A222894.
Sequence in context: A136310 A222868 A222777 * A342411 A231580 A182408
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 08 2013
STATUS
approved