A340698 a(n) is the position of n^2 in the list of perfect powers.

1, 2, 4, 5, 6, 9, 10, 11, 12, 13, 14, 17, 18, 19, 21, 23, 24, 25, 27, 28, 29, 30, 32, 33, 34, 35, 36, 37, 38, 39, 40, 42, 43, 44, 45, 46, 48, 49, 50, 51, 52, 54, 55, 56, 57, 59, 62, 63, 64, 65, 66, 67, 69, 70, 71, 73, 74, 75, 77, 78, 79, 80, 81, 82, 83, 84, 85

Offset

1,2

Links

Hugo Pfoertner, Table of n, a(n) for n = 1..10000

Mathematica

A340698[n_] :=
  First @@ Position[
    Join[{1},
     Select[Range[n^2], GCD @@ FactorInteger[#][[All, 2]] > 1 &]],
    n^2];
Table[A340698[n], {n, 1, 67}] (* Robert P. P. McKone, Jan 17 2021 *)

Prog

(PARI) ispwr(n) = ispower(n) || (n==1); \\ A001597
Vec(select(issquare, select(ispwr, [1..5000]), 1)) \\ Michel Marcus, Jan 18 2021

Crossrefs

Cf. A000290, A001597, A340699.

Sequence in context: A343585 A153242 A143070 * A206926 A005528 A211030

Adjacent sequences: A340695 A340696 A340697 * A340699 A340700 A340701

Keyword

nonn

Author

Hugo Pfoertner, Jan 17 2021

Status

approved