A381698 Numbers of the form (2^k-1)^2 - 2 that are squarefree.

7, 47, 223, 959, 3967, 16127, 261119, 1046527, 4190207, 16769023, 67092479, 268402687, 1073676287, 4294836223, 17179607039, 68718952447, 274876858367, 1099509530623, 4398042316799, 17592177655807, 70368727400447, 281474943156223, 1125899839733759, 4503599493152767, 18014398241046527

Offset: 1

Author

Massimo Kofler, Mar 04 2025

Keywords

• nonn

Crossrefs

Intersection of A093112 and A005117.

Cf. A000225.

Programs

Mathematica

Select[Table[(2^n-1)^2 - 2, {n, 2, 30}], SquareFreeQ] (* Amiram Eldar, Mar 04 2025 *)

PARI

select(issquarefree, vector(30, n, n++; (2^n-1)^2 - 2)) \\ Michel Marcus, Mar 04 2025