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 A205957 a(n) = exp(-Sum_{k=1..n} Sum_{d|k, d prime} moebius(d)*log(k/d)). 5
 1, 1, 1, 1, 2, 2, 12, 12, 48, 144, 1440, 1440, 34560, 34560, 483840, 7257600, 58060800, 58060800, 3135283200, 3135283200, 125411328000, 2633637888000, 57940033536000, 57940033536000, 5562243219456000, 27811216097280000, 723091618529280000, 6507824566763520000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 COMMENTS The author proposes to denote this sequence lcm_{p}(n) as lcm(n) = lcm({1,2,..n}) = exp(Sum_{k=1..n} Sum_{d|k} moebius(d)*log(k/d)). For n > 0 the a(n) are the partial products of A205959(n), which is the exponential of a modified von Mangoldt function where the divisors are restricted to prime divisors. LINKS Peter Luschny, The von Mangoldt Transformation. MAPLE with(numtheory): A205957 := proc(n) simplify(exp(-add(add(mobius(d)*log(k/d), d=select(isprime, divisors(k))), k=1..n))) end: seq(A205957(i), i=0..27); MATHEMATICA a[n_] := Exp[-Sum[ MoebiusMu[p] Log[k/p], {k, 1, n}, {p, FactorInteger[k][[All, 1]]}]]; Table[a[n], {n, 0, 27}] (* Jean-François Alcover, Jun 27 2013 *) PROG (Sage) def A205957(n) : return simplify(exp(-add(add(moebius(p)*log(k/p) for p in prime_divisors(k)) for k in (1..n)))) (PARI) a(n)=prod(k=4, n, my(f=factor(k)[, 1]); prod(i=1, #f, k/f[i])) \\ Charles R Greathouse IV, Jun 27 2013 CROSSREFS Cf. A003418, A205959, A216152, A216153. Sequence in context: A232853 A055772 A025527 * A092144 A224497 A305753 Adjacent sequences:  A205954 A205955 A205956 * A205958 A205959 A205960 KEYWORD nonn AUTHOR Peter Luschny, Sep 01 2012 STATUS approved

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Last modified August 23 11:24 EDT 2019. Contains 326222 sequences. (Running on oeis4.)