OFFSET
1,6
LINKS
Jinyuan Wang, Table of n, a(n) for n = 1..10000
EXAMPLE
The unitary divisors of 12 are {1, 3, 4, 12}, 1 and 3 are smaller than sqrt(12) and their sum is 1 + 3 = 4, hence a(12) = 4.
MATHEMATICA
a[n_] := DivisorSum[n, # &, #^2 < n && CoprimeQ[#, n/#] &]; Array[a, 100]
PROG
(PARI) a(n) = sumdiv(n, d, if(gcd(d, n/d)==1 && d<sqrt(n), d)); \\ Jinyuan Wang, Apr 12 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Apr 12 2020
STATUS
approved