A212716 - OEIS

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

(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 *)