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 A025530 a(n) = (1/1 - 1/2 + ... + (-1)^(n-1)/n)*lcm{1..n}. 4
 1, 1, 5, 7, 47, 37, 319, 533, 1879, 1627, 20417, 18107, 263111, 237371, 261395, 477745, 8842385, 8161705, 167324635, 155685007, 166770367, 156188887, 3825136961, 3602044091, 19081066231, 18051406831, 57128792093, 54260455193, 1653866633797 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..1000 MATHEMATICA nn=30; With[{fr=Accumulate[Table[1/(n (-1)^(n-1)), {n, nn}]]}, Table[fr[[n]] LCM@@ Range[n], {n, nn}]] (* Harvey P. Dale, Dec 27 2012 *) PROG (Haskell) a025530 n = sum \$ map (div (a003418 \$ fromInteger n))                       (zipWith (*) [1..n] a033999_list) -- Reinhard Zumkeller, Dec 23 2011 (PARI) a(n)=my(v=primes(primepi(n)), k=sqrtint(n), L=log(n+.5), t); t=prod(i=1, #v, if(v[i]>k, v[i], v[i]^(L\log(v[i])))); -sum(i=1, n, (-1)^i*t/i) \\ Charles R Greathouse IV, Dec 23 2011 (PARI) s=1; v=vector(10^4, i, 1); for(n=2, #v, t=n/gcd(s, n); s*=t; v[n]=v[n-1]*t-(-1)^n*s/n); v \\ Charles R Greathouse IV, Dec 23 2011 CROSSREFS Cf. A058312, A058313, A003418, A033999. Sequence in context: A058313 A120301 A119787 * A106114 A217039 A299452 Adjacent sequences:  A025527 A025528 A025529 * A025531 A025532 A025533 KEYWORD nonn,easy,nice AUTHOR STATUS approved

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Last modified August 20 21:29 EDT 2019. Contains 326155 sequences. (Running on oeis4.)