A060763 Number of distinct differences between consecutive divisors (ordered by increasing magnitude) of n which are not also divisors of n.

0, 0, 1, 0, 1, 0, 1, 0, 2, 1, 1, 0, 1, 1, 2, 0, 1, 0, 1, 0, 3, 1, 1, 0, 2, 1, 3, 1, 1, 1, 1, 0, 3, 1, 3, 0, 1, 1, 3, 1, 1, 0, 1, 1, 4, 1, 1, 0, 2, 2, 3, 1, 1, 0, 3, 2, 3, 1, 1, 0, 1, 1, 4, 0, 3, 1, 1, 1, 3, 3, 1, 0, 1, 1, 3, 1, 3, 1, 1, 2, 4, 1, 1, 1, 3, 1, 3, 1, 1, 1, 2, 1, 3, 1, 3, 0, 1, 2, 4, 0, 1, 1, 1, 1, 5

Offset

1,9

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

For n=70, divisors={1,2,5,7,10,14,35,70}; differences={1,3,2,3,4,21,35}; the differences {3,4,21} are not divisors, so a(70)=3.

Maple

f:= proc(n) local D, L;
  D:= numtheory:-divisors(n);
  L:= sort(convert(D, list));
  nops(convert(L[2..-1]-L[1..-2], set) minus D);
end proc:
map(f, [$1..200]); # Robert Israel, Jul 03 2017

Mathematica

a[n_] := Length[Complement[Drop[d=Divisors[n], 1]-Drop[d, -1], d]]

Prog

(PARI) a(n) = my(d=divisors(n)); #select(x->(setsearch(d, x)==0), vecsort(vector(#d-1, k, d[k+1] - d[k]), , 8)); \\ Michel Marcus, Jul 04 2017

Crossrefs

Cf. A060682, A060738, A060764.

Sequence in context: A302234 A345007 A026920 * A131576 A341675 A358218

Adjacent sequences: A060760 A060761 A060762 * A060764 A060765 A060766

Keyword

nonn

Author

Labos Elemer, Apr 24 2001

Extensions

Edited by Dean Hickerson, Jan 22 2002

Status

approved