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A306206
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a(n) = Sum_{k=0..n} (n^2)!/((n^2-n*k)!*n!^k).
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2
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1, 2, 13, 3445, 127028721, 1249195963773451, 5343245431687763366112193, 14729376926426500067331714992293420777, 36332859343341728199556523379140726537646663631786369
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) ~ 2 * (n^2)! / (n!)^n.
a(n) ~ n^(n^2 - n/2 + 1) / (exp(1/12) * 2^((n-3)/2) * Pi^((n-1)/2)). (End)
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PROG
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(PARI) {a(n) = sum(k=0, n, (n^2)!/((n^2-n*k)!*n!^k))}
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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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