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 A126884 #14 Aug 10 2021 16:52:14
%S A126884 2,3,9,65,1025,32769,2097153,268435457,68719476737,35184372088833,
%T A126884 36028797018963969,73786976294838206465,302231454903657293676545,
%U A126884 2475880078570760549798248449,40564819207303340847894502572033,1329227995784915872903807060280344577,87112285931760246646623899502532662132737
%N A126884 a(n) = (2^0)*(2^1)*(2^2)*(2^3)...(2^n)+1 = 2^T_n+1 (cf. A000217).
%C A126884 For n>1 every odd/even pair share at least one factor.
%F A126884 a(n) = 2^A000217(n)+1. - _Michel Marcus_, Jul 16 2013
%F A126884 a(n) = A006125(n+1)+1. - _Alois P. Heinz_, Jun 20 2020
%p A126884 a:= n-> 2^(n*(n+1)/2)+1:
%p A126884 seq(a(n), n=0..16); # _Alois P. Heinz_, Jun 20 2020
%t A126884 Table[Times@@(2^Range[0,n])+1,{n,0,20}] (* _Harvey P. Dale_, Aug 10 2021 *)
%o A126884 (PARI) a(n) = prod(k=0, n, 2^k) + 1 \\ _Michel Marcus_, Jul 16 2013
%Y A126884 Cf. A000217, A006125.
%K A126884 nonn,easy
%O A126884 0,1
%A A126884 _Marco Matosic_, Dec 29 2006
%E A126884 a(11) corrected and a(14-16) from _Georg Fischer_, Jun 20 2020