A085428 Sum of the smallest and largest prime divisors of the n-th composite number.

4, 5, 4, 6, 7, 5, 9, 8, 4, 5, 7, 10, 13, 5, 10, 15, 6, 9, 7, 4, 14, 19, 12, 5, 21, 16, 7, 9, 13, 8, 25, 5, 14, 7, 20, 15, 5, 16, 9, 22, 31, 7, 33, 10, 4, 18, 13, 19, 26, 9, 5, 39, 8, 21, 18, 15, 7, 6, 43, 9, 22, 45, 32, 13, 7, 20, 25, 34, 49, 24, 5, 9, 14, 7

Offset: 0

Author

Cino Hilliard, Aug 13 2003

Keywords

• easy
• nonn

Crossrefs

Equals A056608(n) + A052369(n).

Programs

PARI

maxpmindivc(n) = { for(x=4,n, s=0; forstep(p=2,x-1,1, if(x%p==0 & isprime(p),s=p; break); ); forstep(p=x-1,2,-1, if(x%p==0 & isprime(p),print1(s+p,","); break); ) ) }