A212716 Denominator of Sum_{k=1..n} 1/lambda(k), where lambda(k) is the Carmichael's lambda function.

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

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