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A334985
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a(n) = lcm(n, tau(n), sigma(n), pod(n)) / gcd(n, tau(n), sigma(n), pod(n)) where tau(k) is the number of divisors of k (A000005), sigma(k) is the sum of divisors of k (A000203) and pod(k) is the product of divisors of k (A007955).
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1
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1, 6, 12, 168, 30, 18, 56, 960, 351, 450, 132, 6048, 182, 588, 1800, 158720, 306, 25272, 380, 84000, 14112, 2178, 552, 414720, 11625, 7098, 29160, 32928, 870, 405000, 992, 2064384, 17424, 15606, 58800, 917070336, 1406, 10830, 85176, 11520000, 1722, 3111696
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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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a(n) = lcm(tau(n), sigma(n), pod(n)) / gcd(n, tau(n), sigma(n)).
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EXAMPLE
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a(6) = lcm(6, tau(6), sigma(6), pod(6)) / gcd(6, tau(6), sigma(6), pod(6)) = lcm(6, 4, 12, 36) / gcd(6, 4, 12, 36) = 36 / 2 = 18.
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MATHEMATICA
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a[n_] := LCM @@ {(d = DivisorSigma[0, n]), (s = DivisorSigma[1, n]), n^(d/2)} / GCD @@ {n, d, s}; Array[a, 50] (* Amiram Eldar, Sep 22 2020 *)
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PROG
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(Magma) [LCM([#Divisors(n), &+Divisors(n), &*Divisors(n)]) / GCD([#Divisors(n), &+Divisors(n), &*Divisors(n)]): n in [1..100]]
(PARI) a(n) = my(f=factor(n), v=[n, numdiv(f), sigma(f), vecprod(divisors(f))]); lcm(v)/gcd(v); \\ Michel Marcus, Sep 22 2020
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CROSSREFS
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Cf. A329929 (lcm(tau(n), sigma(n), pod(n)) / gcd(tau(n), sigma(n), pod(n))).
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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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