login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A085085 Numerator of Sum_{i=2..t} (d(i)/d(i-1)-1), where d(1), ..., d(t) are the divisors of n. 2
0, 1, 2, 2, 4, 5, 6, 3, 4, 7, 10, 10, 12, 9, 14, 4, 16, 4, 18, 17, 16, 13, 22, 25, 8, 15, 6, 19, 28, 68, 30, 5, 20, 19, 42, 14, 36, 21, 22, 51, 40, 31, 42, 23, 92, 25, 46, 5, 12, 6, 26, 25, 52, 11, 46, 79, 28, 31, 58, 157, 60, 33, 146, 6, 48, 35, 66, 29, 32, 218, 70, 131, 72, 39, 22, 31, 88 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..77.

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)); numerator(sum(i=2, #d, d[i]/d[i-1] - 1)); \\ Michel Marcus, Feb 25 2015

CROSSREFS

Cf. A085091.

Sequence in context: A261665 A208096 A049269 * A121600 A126870 A137413

Adjacent sequences:  A085082 A085083 A085084 * A085086 A085087 A085088

KEYWORD

nonn,frac

AUTHOR

N. J. A. Sloane, Aug 11 2003

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified February 24 12:59 EST 2018. Contains 299623 sequences. (Running on oeis4.)