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A218073
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Number of profiles in domino tiling of a 2*n checkboard.
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1
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0, 1, 2, 9, 12, 50, 60, 245, 280, 1134, 1260, 5082, 5544, 22308, 24024, 96525, 102960, 413270, 437580, 1755182, 1847560, 7407036, 7759752, 31097794, 32449872, 130007500, 135207800, 541574100, 561632400, 2249204040, 2326762800, 9316746045, 9617286240, 38504502630
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OFFSET
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0,3
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LINKS
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FORMULA
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If n is even, a(n) = binomial(n, n/2)*n/2.
If n is odd, a(n) = binomial(n + 1, (n + 1)/2)*n/2.
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MAPLE
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a:= proc(n) option remember;
`if`(n<3, n, (n*(5-7*n)*a(n-1) +4*(n-2)*(7*n+16)*a(n-3)
+(24-12*n+172*n^2)*a(n-2))/ ((n+1)*(43*n-89)))
end:
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MATHEMATICA
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PROG
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(Maxima) a[0]:0$a[1]:1$a[2]:2$
a[n]:=(n*(5-7*n)*a[n-1] +4*(n-2)*(7*n+16)*a[n-3]+(24-12*n+172*n^2)*a[n-2])/ ((n+1)*(43*n-89))$
makelist(a[n] , n, 0, 40); /* Martin Ettl, Oct 21 2012 */
(PARI) a(n) = n/2 * binomial(n+(n%2), (n+n%2)/2); /* Joerg Arndt, Oct 21 2012 */
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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