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A269932
Number of n X 2 0..6 arrays with some element plus some horizontally, diagonally, antidiagonally or vertically adjacent neighbor totalling six exactly once.
1
7, 900, 36312, 1213836, 36926640, 1064495604, 29614748232, 803524526172, 21398721760608, 561711817333572, 14576385809307384, 374729873865609900, 9558865762690235664, 242237150160785521812, 6104272703188011708840
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 30*a(n-1) + 159*a(n-2) - 5480*a(n-3) - 41064*a(n-4) - 53760*a(n-5) - 19600*a(n-6) for n>7.
Empirical g.f.: x*(7 + 690*x + 8199*x^2 + 19736*x^3 - 42600*x^4 + 20160*x^5 + 2800*x^6) / (1 - 15*x - 192*x^2 - 140*x^3)^2. - Colin Barker, Jan 29 2019
EXAMPLE
Some solutions for n=3:
..3..5. .1..6. .3..4. .0..2. .4..6. .1..0. .6..2. .2..5. .1..3. .3..0
..3..2. .0..3. .5..4. .4..1. .4..5. .6..3. .6..2. .3..5. .2..0. .5..3
..1..1. .4..4. .4..1. .3..6. .3..2. .2..2. .5..4. .0..3. .6..5. .2..2
CROSSREFS
Column 2 of A269937.
Sequence in context: A330295 A177908 A127102 * A352401 A252175 A038808
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 08 2016
STATUS
approved