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A076398 Number of distinct prime factors of n-th perfect power. 3
0, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 2, 2, 1, 1, 1, 2, 1, 1, 2, 2, 2, 1, 1, 2, 1, 2, 1, 2, 1, 3, 1, 2, 1, 2, 2, 2, 2, 1, 1, 2, 2, 2, 1, 2, 3, 1, 2, 2, 1, 2, 1, 1, 1, 2, 1, 2, 2, 2, 2, 1, 2, 2, 1, 2, 2, 2, 2, 1, 3, 1, 2, 2, 1, 2, 3, 1, 2, 2, 3, 1, 1, 2, 1, 2, 2, 2, 2, 2, 3, 1, 2, 1, 2, 1, 1, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,9
LINKS
Eric Weisstein's World of Mathematics, Perfect Powers.
Eric Weisstein's World of Mathematics, Distinct Prime Factors.
FORMULA
a(n) = A001221(A001597(n)).
a(n) = A001221(A025478(n)).
MATHEMATICA
ppQ[1] = True; ppQ[n_] := GCD @@ FactorInteger[n][[All, 2]] > 1; PrimeNu /@ Select[Range[10^4], ppQ] (* Jean-François Alcover, Jul 15 2017 *)
PROG
(Haskell)
a076398 = a001221 . a025478 -- Reinhard Zumkeller, Mar 28 2014
(PARI) lista(nn) = for(n=1, nn, if ((n==1) || ispower(n), print1(omega(n), ", "))); \\ Michel Marcus, Jul 15 2017
CROSSREFS
Sequence in context: A205788 A214054 A330739 * A086257 A161098 A354999
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Oct 09 2002
STATUS
approved

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Last modified March 29 10:44 EDT 2024. Contains 371268 sequences. (Running on oeis4.)