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

Author

Michel Lagneau, May 25 2012

Keywords

• nonn
• frac

Examples

			1, 2, 5/2, 3, 13/4, 15/4, 47/12, 53/12, 55/12, 29/6, 74/15, 163/30, ...
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A002322, A048049, A211306 (numerator).

Programs

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 *)