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 A383065 #21 May 01 2025 21:52:49
%S A383065 2,3,4,5,7,9,12,13,16,17,18,19,27,31,36,50,60,61,64,80,89,107,108,112,
%T A383065 127,135,147,189,200,212,243,252,343,448,464,500,521,576,600,607,612,
%U A383065 648,675,688,756,768,784,800,832,875,900,1058,1212,1279,1280
%N A383065 Integers k such that (k/rad(k))*2^rad(k) - 1 is prime where rad = A007947.
%e A383065 12 is a term because (12/6)*2^6 - 1 = 127 is prime, where d = 6 is largest squarefree divisor d of k = 12.
%t A383065 s={};Do[r=Last[Select[Divisors[n], SquareFreeQ]];If[PrimeQ[2^r*n/r-1],AppendTo[s,n]],{n,1280}];s (* _James C. McMahon_, May 01 2025 *)
%o A383065 (Magma) [k: k in [1..1300] | IsPrime((k div &*PrimeDivisors(k))*2^&*PrimeDivisors(k)-1)];
%o A383065 (PARI) isok(k) = my(r=factorback(factorint(k)[, 1])); ispseudoprime((k/r)*2^r - 1); \\ _Michel Marcus_, Apr 20 2025
%Y A383065 Supersequence of A000043 and A172461.
%Y A383065 Cf. A002234, A003557, A007947.
%K A383065 nonn
%O A383065 1,1
%A A383065 _Juri-Stepan Gerasimov_, Apr 19 2025