A104527 Denominator of sum(1/(phi(k)sigma(k)),k=1..n), where phi(k) is the totient function and sigma(k) is the sum of the divisors function.

1, 3, 24, 168, 7, 168, 112, 1680, 21840, 65520, 65520, 16380, 32760, 21840, 29120, 902720, 8124480, 8124480, 1624896, 1624896, 3249792, 5416320, 59579520, 59579520, 59579520, 178738560, 178738560, 178738560, 178738560, 178738560

Offset

1,2

Comments

The first 5 sums are: 1,4/3,35/24,257/168,11/7.

Links

Table of n, a(n) for n=1..30.

Example

a(3)=24 because phi(1)*sigma(1)+phi(2)*sigma(2)+phi(3)*sigma(3)=1/(1*1)+1/(1*3)+1/(2*4)=35/24.

Maple

with(numtheory): a:=n->denom(sum(1/phi(k)/sigma(k), k=1..n)): seq(a(n), n=1..35);

Crossrefs

Cf. A104526, A093827.

Sequence in context: A094432 A354677 A354678 * A058038 A089697 A120741

Adjacent sequences: A104524 A104525 A104526 * A104528 A104529 A104530

Keyword

frac,nonn

Author

Emeric Deutsch, Mar 12 2005

Status

approved