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A028576
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a(n) = (1/(4*n)) * Sum_{d|n} mu(n/d) * binomial(2*d, d)^2.
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1
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1, 4, 33, 304, 3175, 35556, 420665, 5176000, 65664000, 853367900, 11309870605, 152342891952, 2080240006923, 28738242567524, 401024083514775, 5645275548076800, 80084088088568947, 1143862232096407392, 16437995698573558421, 237520818846111947600
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OFFSET
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1,2
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LINKS
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PROG
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(PARI) a(n) = sumdiv(n, d, moebius(n/d)*binomial(2*d, d)^2)/(4*n) \\ Michel Marcus, Jun 15 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Lionel Levine (levine(AT)ultranet.com)
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STATUS
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approved
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