This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A381698 #14 Mar 09 2025 13:17:51
%S A381698 7,47,223,959,3967,16127,261119,1046527,4190207,16769023,67092479,
%T A381698 268402687,1073676287,4294836223,17179607039,68718952447,274876858367,
%U A381698 1099509530623,4398042316799,17592177655807,70368727400447,281474943156223,1125899839733759,4503599493152767,18014398241046527
%N A381698 Numbers of the form (2^k-1)^2 - 2 that are squarefree.
%t A381698 Select[Table[(2^n-1)^2 - 2, {n, 2, 30}], SquareFreeQ] (* _Amiram Eldar_, Mar 04 2025 *)
%o A381698 (PARI) select(issquarefree, vector(30, n, n++; (2^n-1)^2 - 2)) \\ _Michel Marcus_, Mar 04 2025
%Y A381698 Intersection of A093112 and A005117.
%Y A381698 Cf. A000225.
%K A381698 nonn
%O A381698 1,1
%A A381698 _Massimo Kofler_, Mar 04 2025