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

Author

Michel Lagneau, May 25 2012

Keywords

• nonn
• frac

Examples

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

Crossrefs

Cf. A000203, A212717.

Programs

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}]]