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 A268617 a(n) = (1/n^2) * Sum_{d|n} moebius(n/d)*binomial(3*d,d). 3
 3, 3, 9, 30, 120, 513, 2373, 11484, 57861, 300420, 1599477, 8692074, 48061689, 269694453, 1532744100, 8808000696, 51110965698, 299155382325, 1764498529977, 10479611189400, 62629105220514, 376411503694677, 2273982941083533, 13802537605619124, 84141675425838225, 514987312014416553, 3163620641291970255 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 2*a(n) is divisible by n (cf. A268618). LINKS FORMULA a(n) = (1/n^2)* Sum_{d|n} A008683(n/d)*A005809(d). a(n) = A060170(n) / n = A268618(n)*n/2. PROG (PARI) { a(n) = sumdiv(n, d, moebius(n/d)*binomial(3*d, d))/n^2; } CROSSREFS Cf. A268618, A268619. Sequence in context: A029857 A327712 A257611 * A264412 A202889 A257620 Adjacent sequences:  A268614 A268615 A268616 * A268618 A268619 A268620 KEYWORD nonn AUTHOR Max Alekseyev, Feb 09 2016 STATUS approved

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Last modified April 1 04:58 EDT 2020. Contains 333155 sequences. (Running on oeis4.)