A081217 - OEIS

%I #11 Mar 08 2019 05:49:43

%S 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 59,61,62,67,71,73,79,79,83,89,97,101,103,107,109,113,119,123,127,127,

%U 131,137,139,149,151,157,163,167,167,173,179,181,191,193,197,199,211,223

%N Greatest squarefree number not exceeding n-th prime power.

%C a(n) = A070321(A000961(n)).

%H Robert Israel, <a href="/A081217/b081217.txt">Table of n, a(n) for n = 1..10000</a>

%p n:= 0:

%p for m from 1 while n <= 100 do

%p   if numtheory:-issqrfree(m) then s:= m fi;

%p   if nops(numtheory:-factorset(m)) <= 1 then n:= n+1; A[n]:= s fi

%p od:

%p seq(A[i],i=1..100); # _Robert Israel_, Jan 08 2018

%t nmax = 100; coeff = 5;

%t A000961 = Join[{1}, Select[Range[2, coeff*nmax],PrimePowerQ]];

%t a070321[n_] := For[k = n, True, k--, If[SquareFreeQ[k], Return[k]]];

%t a[n_] := If[n > Length[A000961], Print["error: increase insufficient coeff ", coeff], a070321[A000961[[n]] ] ];

%t Array[a, nmax] (* _Jean-François Alcover_, Mar 08 2019 *)

%Y Cf. A081218.

%Y Cf. A156898, A156899, A156900, A005117, A000961

%K nonn

%O 1,2

%A _Reinhard Zumkeller_, Mar 10 2003