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%I #27 Jul 15 2023 05:42:03
%S 2,2,3,2,5,3,2,7,2,3,11,5,2,13,3,2,17,7,19,2,23,5,3,29,31,2,11,37,41,
%T 43,2,3,13,47,7,53,5,59,61,2,67,17,71,73,79,3,19,83,89,2,97,101,103,
%U 107,109,23,113,11,5,127,2,7,131,137,139,3,149,151,29,157,163,167,13,31,173,179
%N Prime root of n-th nontrivial prime power (A025475, A246547).
%p cvm := proc(n, level) local f,opf; if n < 2 then RETURN() fi;
%p f := ifactors(n); opf := op(1,op(2,f)); if nops(op(2,f)) > 1 or
%p op(2,opf) <= level then RETURN() fi; op(1,opf) end:
%p A025476_list := n -> seq(cvm(i,1),i=1..n); # n is search limit
%p A025476_list(30000); # _Peter Luschny_, Sep 21 2011
%p # Alternative:
%p isA246547 := n -> n > 1 and not isprime(n) and type(n, 'primepower'):
%p seq(ifactors(p)[2][1][1], p in select(isA246547, [$1..30000])); # _Peter Luschny_, Jul 15 2023
%t Transpose[ Flatten[ FactorInteger[ Select[ Range[2, 30000], !PrimeQ[ # ] && Mod[ #, # - EulerPhi[ # ]] == 0 &]], 1]][[1]] (* _Robert G. Wilson v_ *)
%o (PARI) forcomposite(n=4,10^5,if( ispower(n, , &p) && isprime(p), print1(p,", "))) \\ _Joerg Arndt_, Sep 11 2021
%Y Cf. A025473, A025475, A048148, A246547.
%K easy,nonn
%O 1,1
%A _David W. Wilson_
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