OFFSET
1,6
EXAMPLE
a(12)=3 because the divisors of 12 are: [1, 2, 3, 4, 6, 12] and 2, 3 and 1+2=3 are primes.
a(98)=5 because the divisors of 98 are: [1, 2, 7, 14, 49, 98] and 2, 7, 1+4=5, 4+9=13 and 9+8=17 are primes.
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Jason Earls, May 24 2004
STATUS
approved