OFFSET
1,3
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = A023890(n^2 + 1). - R. J. Mathar, Aug 14 2011
EXAMPLE
a(3) = 11 because 3^2 + 1 = 10 with the divisors {1, 2, 5, 10}, and the sum of the nonprime divisors is 1 + 10 = 11.
MATHEMATICA
Array[ Plus @@ (Select[ Divisors[#^2+1], (!PrimeQ[#])& ])&, 75 ]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Michel Lagneau, Aug 12 2011
STATUS
approved