OFFSET
1,2
PROG
(PARI) is(n)=my(f=factor(n)[, 1], r=prod(i=1, #f, f[i])); r-n/r*prod(i=1, #f, f[i]-1)<=1 \\ Charles R Greathouse IV, Feb 21 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Apr 10 2003
STATUS
approved