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A111601
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Exponential (binomial) convolution of A001818 (with interspersed zeros) and A000142 (factorials).
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1
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1, 2, 9, 36, 225, 1350, 11025, 88200, 893025, 8930250, 108056025, 1296672300, 18261468225, 255660555150, 4108830350625, 65741285610000, 1187451971330625, 21374135483951250, 428670161650355625, 8573403233007112500
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OFFSET
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1,2
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LINKS
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FORMULA
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E.g.f.: (1/sqrt(1-x^2))*x/(1-x).
a(n) = n!*Sum_{k=0..floor((n-1)/2)} binomial(2*k, k)/(4^k).
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CROSSREFS
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Second column (m=1) of triangle |A111595|.
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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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