A085091 Denominator of Sum_{i=2..t} (d(i)/d(i-1)-1), where d(1), ..., d(t) are the divisors of n.

1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 3, 1, 2, 3, 1, 1, 1, 1, 4, 3, 2, 1, 6, 1, 2, 1, 4, 1, 15, 1, 1, 3, 2, 5, 3, 1, 2, 3, 10, 1, 6, 1, 4, 15, 2, 1, 1, 1, 1, 3, 4, 1, 2, 5, 14, 3, 2, 1, 30, 1, 2, 21, 1, 5, 6, 1, 4, 3, 35, 1, 24, 1, 2, 3, 4, 7, 6, 1, 20, 1, 2, 1, 7, 5, 2, 3, 8, 1, 45, 7, 4, 3, 2, 5, 6, 1, 1, 9, 2, 1

Offset

1,6

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

M. D. Vose, Integers with consecutive divisors in small ratio, J. Number Theory, 19 (1984), 233-238.

Example

0, 1, 2, 2, 4, 5/2, 6, 3, 4, 7/2, 10, 10/3, 12, 9/2, 14/3, ...

Maple

with(numtheory): f := proc(n) local t1, t2, t3, i; t1 := divisors(n); t3 := convert(t1, list); t2 := 0; for i from 2 to nops(t3) do t2 := t2+(t3[i]/t3[i-1]-1); od; t2; end;

Prog

(PARI) my(d = divisors(n)); denominator(sum(i=2, #d, d[i]/d[i-1] - 1)); \\ Michel Marcus, Feb 25 2015

Crossrefs

Cf. A085085.

Sequence in context: A068347 A284556 A025865 * A345994 A052128 A284600

Adjacent sequences: A085088 A085089 A085090 * A085092 A085093 A085094

Keyword

nonn,frac

Author

N. J. A. Sloane, Aug 11 2003

Status

approved