OFFSET
1,1
COMMENTS
Greatest common divisor of all prime-exponents in canonical factorization of n-th perfect power. - Reinhard Zumkeller, Oct 13 2002
Asymptotically, 100% of the terms are 2, since the density of cubes and higher powers among the squares and higher powers is 0. - Daniel Forgues, Jul 22 2014
LINKS
Daniel Forgues, Table of n, a(n) for n=1..10000
FORMULA
MAPLE
N:= 10^6: # to get terms corresponding to all perfect powers <= N
V:= Vector(N, storage=sparse);
V[1]:= 2:
for p from 2 to ilog2(N) do
V[[seq(i^p, i=2..floor(N^(1/p)))]]:= p
od:
r, c, A := ArrayTools:-SearchArray(V):
convert(A, list); # Robert Israel, Apr 25 2017
MATHEMATICA
Prepend[DeleteCases[#, 0], 2] &@ Table[If[Set[e, GCD @@ #[[All, -1]]] > 1, e, 0] &@ FactorInteger@ n, {n, 10^4}] (* Michael De Vlieger, Apr 25 2017 *)
PROG
(Haskell)
a025479 n = a025479_list !! (n-1) -- a025479_list is defined in A001597.
-- Reinhard Zumkeller, Mar 28 2014, Jul 15 2012
(PARI) print1(2, ", "); for(k=2, 3^8, if(j=ispower(k), print1(j, ", "))) \\ Hugo Pfoertner, Jan 01 2019
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
EXTENSIONS
Definition corrected by Daniel Forgues, Mar 07 2009
STATUS
approved