OFFSET
1,2
COMMENTS
The quotient c is square for k=1 (trivially), and also k=3518511 (with sum 1861292319 and c=529).
a(30) > 10^11. - Donovan Johnson, Jun 07 2011
EXAMPLE
For k=3 we have (1^2 + 2^2 + 3^2)/3 = 3 so k=3 belongs to the sequence.
PROG
(Sage)
def A186452_yield(upto):
s = 0
for n in IntegerRange(1, upto+1):
s += number_of_divisors(n)**2
if n.divides(s): yield n # D. S. McNeil, Feb 22 2011
(PARI) s=0; for(n=1, 1e7, if((s+=numdiv(n)^2)%n==0, print1(n", "))) \\ Charles R Greathouse IV, Feb 22 2011
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Ctibor O. Zizka, Feb 22 2011
EXTENSIONS
a(24)-a(29) from Donovan Johnson, Jun 07 2011
STATUS
approved