A283919 The smallest square referenced in A013929 (Numbers that are not squarefree).

4, 4, 9, 4, 4, 9, 4, 4, 25, 9, 4, 4, 4, 4, 4, 9, 4, 49, 25, 4, 9, 4, 4, 9, 4, 4, 4, 25, 4, 4, 9, 4, 4, 9, 4, 4, 49, 9, 4, 4, 4, 4, 4, 9, 4, 121, 4, 25, 9, 4, 4, 9, 4, 4, 4, 49, 4, 25, 4, 9, 4, 4, 9, 4, 4, 169, 9, 4, 25, 4, 4, 4, 4, 9, 4, 4, 9, 4, 4, 9, 4, 4

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Robert Price)

Example

A013929(4) = 12, 12 = 2*2*3, so 12 is not squarefree, the square being 2*2 = 4.

Mathematica

s[n_] := If[(pos = Position[(f = FactorInteger[n])[[;; , 2]], _?(# >= 2 &)]) == {}, 1, f[[pos[[1, 1]], 1]]]; Select[Array[s, 250], # > 1 &]^2 (* Amiram Eldar, Nov 14 2020 *)

Prog

(PARI) f(n) = fordiv(n, d, if ((d>1) && issquare(d), return (d))); return (1);
apply(f, select(x->!issquarefree(x), [1..200])) \\ Michel Marcus, Nov 14 2020

Crossrefs

Cf. A013929, A046027.

Sequence in context: A068340 A097667 A202388 * A283670 A019627 A137617

Adjacent sequences: A283916 A283917 A283918 * A283920 A283921 A283922

Keyword

nonn

Author

Robert Price, Mar 17 2017

Status

approved