OFFSET
1,1
COMMENTS
Except for a(2)=6, these are proper prime powers, i.e., numbers p^k where k>1, p prime (A025475). - M. F. Hasler, Feb 12 2012
FORMULA
a(n) = A025475(n) for n>2 (conjectured). - M. F. Hasler, Feb 12 2012
PROG
(PARI) for(n=1, 1e4, A123709(n)==4 & print1(n", ")) \\ M. F. Hasler, Feb 12 2012
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Paul D. Hanna, Oct 09 2006
STATUS
approved