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A081217 Greatest squarefree number not exceeding n-th prime power.

%I A081217 #11 Mar 08 2019 05:49:43
%S A081217 1,2,3,3,5,7,7,7,11,13,15,17,19,23,23,26,29,31,31,37,41,43,47,47,53,
%T A081217 59,61,62,67,71,73,79,79,83,89,97,101,103,107,109,113,119,123,127,127,
%U A081217 131,137,139,149,151,157,163,167,167,173,179,181,191,193,197,199,211,223
%N A081217 Greatest squarefree number not exceeding n-th prime power.
%C A081217 a(n) = A070321(A000961(n)).
%H A081217 Robert Israel, <a href="/A081217/b081217.txt">Table of n, a(n) for n = 1..10000</a>
%p A081217 n:= 0:
%p A081217 for m from 1 while n <= 100 do
%p A081217   if numtheory:-issqrfree(m) then s:= m fi;
%p A081217   if nops(numtheory:-factorset(m)) <= 1 then n:= n+1; A[n]:= s fi
%p A081217 od:
%p A081217 seq(A[i],i=1..100); # _Robert Israel_, Jan 08 2018
%t A081217 nmax = 100; coeff = 5;
%t A081217 A000961 = Join[{1}, Select[Range[2, coeff*nmax],PrimePowerQ]];
%t A081217 a070321[n_] := For[k = n, True, k--, If[SquareFreeQ[k], Return[k]]];
%t A081217 a[n_] := If[n > Length[A000961], Print["error: increase insufficient coeff ", coeff], a070321[A000961[[n]] ] ];
%t A081217 Array[a, nmax] (* _Jean-François Alcover_, Mar 08 2019 *)
%Y A081217 Cf. A081218.
%Y A081217 Cf. A156898, A156899, A156900, A005117, A000961
%K A081217 nonn
%O A081217 1,2
%A A081217 _Reinhard Zumkeller_, Mar 10 2003