OFFSET
1,2
COMMENTS
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
EXAMPLE
36 = 2^2*3^2 with both exponents being equal is not in the sequence.
PROG
(PARI) isok(n) = {my(f = factor(n)); my(nbf = #f~); if (prod(i=1, nbf, prime(i)) ! = prod(i=1, nbf, f[i, 1]), return (0)); for (j=2, nbf, if (f[j, 2] <= f[j-1, 2], return (0)); ); return (1); } \\ Michel Marcus, Jun 04 2014
(Haskell)
import Data.Set (singleton, deleteFindMin, insert)
a133809 n = a133809_list !! (n-1)
a133809_list = 1 : f (singleton (2, 2, 1)) where
f s = y : f (insert (y*p, p, e+1) $ insert (y*q^(e+1), q, e+1) s')
where q = a151800 p
((y, p, e), s') = deleteFindMin s
-- Reinhard Zumkeller, Apr 14 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Olivier Gérard, Sep 23 2007
STATUS
approved