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 A246699 #30 Feb 07 2025 12:21:53
%S A246699 1,2,3,6,11,21,29,31,51,55,57
%N A246699 Squarefree n such that C(2^n - 1, n) is also squarefree, where C is the binomial coefficient.
%C A246699 Conjectured to be finite.
%C A246699 The subsequence of squarefree numbers in A245569. - _M. F. Hasler_, Nov 28 2014
%t A246699 Select[Range[100], SquareFreeQ[#] && SquareFreeQ[Binomial[2^# - 1, #]] &] (* _Vincenzo Librandi_, Nov 14 2014 *)
%t A246699 Select[Range[60],AllTrue[{#,Binomial[2^#-1,#]},SquareFreeQ]&] (* _Harvey P. Dale_, Feb 07 2025 *)
%o A246699 (Magma) [n: n in [1..200] | IsSquarefree(n) and IsSquarefree(Binomial(2^n-1, n))];
%o A246699 (PARI) is(n)=issquarefree(n) && issquarefree(binomial(2^n-1,n)) \\ _Charles R Greathouse IV_, Nov 16 2014
%Y A246699 Cf. A000225, A005117, A136556.
%K A246699 nonn
%O A246699 1,2
%A A246699 _Juri-Stepan Gerasimov_, Nov 15 2014