OFFSET
1,3
COMMENTS
The middle divisors of n, are the divisors in the half-open interval [sqrt(n/2), sqrt(n*2)).
EXAMPLE
For n = 12 the 12th number that has middle divisors is 24. The divisors of 24 are 1, 2, 3, 4, 6, 8, 12, 24. The middle divisors of 24 are 4 and 6, and the sum of them is 4 + 6 = 10, so a(12) = 10.
PROG
(PARI) lista(nn) = for (n=1, nn, if (s=sumdiv(n, d, if(d^2>=n/2 && d^2<2*n, d, 0)), print1(s, ", "))); \\ Michel Marcus, Apr 24 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Omar E. Pol, Apr 07 2018
STATUS
approved