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 A212716 Denominator of Sum_{k=1..n} 1/lambda(k), where  lambda(k) is the Carmichael's lambda function. 2
 1, 1, 2, 1, 4, 4, 12, 12, 12, 6, 15, 30, 60, 60, 15, 60, 240, 80, 720, 720, 720, 720, 7920, 7920, 1584, 1584, 1584, 1584, 11088, 11088, 55440, 55440, 55440, 13860, 6930, 3465, 13860, 13860, 6930, 13860, 27720, 27720, 27720, 27720, 27720, 27720, 637560, 637560 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 EXAMPLE 1, 2, 5/2, 3, 13/4, 15/4, 47/12, 53/12, 55/12, 29/6, 74/15, 163/30, ... MAPLE with(numtheory): a:=n->denom(sum(1/lambda(k), k=1..n)): seq(a(n), n=1..50); MATHEMATICA Denominator[Table[Sum[1/CarmichaelLambda[k], {k, 1, n}], {n, 1, 50}]] Denominator @ Accumulate @ Table[1/CarmichaelLambda[n], {n, 1, 50}] (* Amiram Eldar, Sep 19 2019 *) CROSSREFS Cf. A002322, A048049, A211306 (numerator). Sequence in context: A209478 A211178 A048049 * A057772 A145861 A191660 Adjacent sequences:  A212713 A212714 A212715 * A212717 A212718 A212719 KEYWORD nonn,frac AUTHOR Michel Lagneau, May 25 2012 STATUS approved

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Last modified August 13 22:57 EDT 2020. Contains 336473 sequences. (Running on oeis4.)