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

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, 59, 61, 62, 67, 71, 73, 79, 79, 83, 89, 97, 101, 103, 107, 109, 113, 119, 123, 127, 127, 131, 137, 139, 149, 151, 157, 163, 167, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223

Offset: 1

Author

Reinhard Zumkeller, Mar 10 2003

Keywords

• nonn

Comments

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

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A081218.

Cf. A156898, A156899, A156900, A005117, A000961

Programs

Maple

n:= 0:
for m from 1 while n <= 100 do
  if numtheory:-issqrfree(m) then s:= m fi;
  if nops(numtheory:-factorset(m)) <= 1 then n:= n+1; A[n]:= s fi
od:
seq(A[i],i=1..100); # Robert Israel, Jan 08 2018

Mathematica

nmax = 100; coeff = 5;
A000961 = Join[{1}, Select[Range[2, coeff*nmax],PrimePowerQ]];
a070321[n_] := For[k = n, True, k--, If[SquareFreeQ[k], Return[k]]];
a[n_] := If[n > Length[A000961], Print["error: increase insufficient coeff ", coeff], a070321[A000961[[n]] ] ];
Array[a, nmax] (* Jean-François Alcover, Mar 08 2019 *)