OFFSET
1,1
EXAMPLE
a(1)=3 since sigma(3)/3=(1+3)/3=1+1/3.
a(2)=12 since sigma(12)/12=(1+2+3+4+6+12)/12=28/12=7/3=2+1/3.
PROG
(PARI) is(n)=denominator(sigma(n, -1)-1/3)==1 \\ Charles R Greathouse IV, Mar 09 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
J.C. Klein (hklein(AT)planet.nl), May 08 2009
EXTENSIONS
a(11)-a(16) from Donovan Johnson, May 26 2009
a(17)-a(23) from Michel Marcus, Sep 21 2012
STATUS
approved