OFFSET
1,9
EXAMPLE
n=27: gcd(2+3,27)=1, gcd(3+5,27)=1, gcd(5+7,27)=3, gcd(7+11,27)=9, gcd(11+13,27)=3, hence a(27)=2.
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Oct 14 2002
STATUS
approved