A212718 Denominator of Sum_{k=1..n} 1/sigma(k).

1, 3, 12, 84, 28, 42, 168, 280, 3640, 32760, 32760, 32760, 4680, 1170, 4680, 145080, 145080, 145080, 145080, 1015560, 4062240, 4062240, 4062240, 4062240, 4062240, 4062240, 4062240, 4062240, 4062240, 4062240, 2031120, 2031120, 1015560, 3046680, 6093360, 6093360

Offset

1,2

Links

Table of n, a(n) for n=1..36.

Example

1, 4/3, 19/12, 145/84, 53/28, 83/42, 353/168, …

Maple

with(numtheory): a:=n->numer(sum(1/sigma(k), k=1..n)): seq(a(n), n=1..50);

Mathematica

Denominator[Table[Sum[1/DivisorSigma[1, k], {k, 1, n}], {n, 1, 50}]]

Crossrefs

Cf. A000203, A212717.

Sequence in context: A067111 A171186 A229421 * A357846 A051549 A245775

Adjacent sequences: A212715 A212716 A212717 * A212719 A212720 A212721

Keyword

nonn,frac

Author

Michel Lagneau, May 25 2012

Status

approved