cp's OEIS Frontend

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

%I A085091 #10 Sep 07 2018 04:41:07
%S A085091 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,
%T A085091 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,
%U A085091 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
%N A085091 Denominator of Sum_{i=2..t} (d(i)/d(i-1)-1), where d(1), ..., d(t) are the divisors of n.
%H A085091 Antti Karttunen, <a href="/A085091/b085091.txt">Table of n, a(n) for n = 1..65537</a>
%H A085091 M. D. Vose, <a href="http://dx.doi.org/10.1016/0022-314X(84)90107-0">Integers with consecutive divisors in small ratio</a>, J. Number Theory, 19 (1984), 233-238.
%e A085091 0, 1, 2, 2, 4, 5/2, 6, 3, 4, 7/2, 10, 10/3, 12, 9/2, 14/3, ...
%p A085091 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;
%o A085091 (PARI) my(d = divisors(n)); denominator(sum(i=2, #d, d[i]/d[i-1] - 1)); \\ _Michel Marcus_, Feb 25 2015
%Y A085091 Cf. A085085.
%K A085091 nonn,frac
%O A085091 1,6
%A A085091 _N. J. A. Sloane_, Aug 11 2003