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

1,2

Comments

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

Links

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

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 *)

Crossrefs

Cf. A081218.

Cf. A156898, A156899, A156900, A005117, A000961

Sequence in context: A214034 A343224 A047844 * A335139 A320036 A053271

Adjacent sequences: A081214 A081215 A081216 * A081218 A081219 A081220

Keyword

nonn

Author

Reinhard Zumkeller, Mar 10 2003

Status

approved