OFFSET
1,1
COMMENTS
Successively greater values of a(n) occur when 2n+1 is prime.
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
FORMULA
A060680(2n+1)
EXAMPLE
For n=38, 2n+1=77; divisors={1,7,11,77}; differences={6,4,66}; a(38) = smallest difference = 4.
MATHEMATICA
a[n_ ] := Min@@(Drop[d=Divisors[2n+1], 1]-Drop[d, -1])
Array[Min[Differences[Divisors[2*#+1]]]&, 80] (* Harvey P. Dale, Dec 08 2013 *)
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Apr 19 2001
EXTENSIONS
Edited by Dean Hickerson, Jan 22 2002
STATUS
approved