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A059487
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Number of 2-enumeration of 4n X 4n quarter-turn symmetric alternating-sign matrices.
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1
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1, 2, 80, 53760, 590413824, 104981650735104, 300931721514121691136, 13874404129378738693891686400, 10274196157891080769280680484929536000, 122089077024940067215877965611538507917950976000, 23266604385482749027479729551862778584550130343015874560000
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OFFSET
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0,2
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LINKS
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MAPLE
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A059487 := proc(n) local i, j, t1; t1 := (-1)^(n*(n-1)/2)*2^(2*n^2-n); for i to n do for j to n do t1 := t1*(4*j - 4*i + 1)/(j - i + n); end do end do; t1 end proc;
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MATHEMATICA
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a[n_] := Module[{t1 = (-1)^(n*(n - 1)/2)*2^(2*n^2 - n)}, Do[t1 = t1*(4*j - 4*i + 1)/(j - i + n), {j, n}, {i, n}]; t1];
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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