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 A254429 #15 Mar 26 2023 12:45:25
%S A254429 0,2,5,33,8589934593
%N A254429 a(0) = 0; for n >= 0, a(n+1) = 2^a(n) + 1.
%F A254429 a(n+1) = A000051(a(n)). - _Reinhard Zumkeller_, Jan 31 2015
%t A254429 RecurrenceTable[{a[0]==0, a[n]==2^a[n-1] + 1}, a, {n, 5}] (* _Vincenzo Librandi_, Feb 01 2015 *)
%t A254429 NestList[2^#+1&,0,4] (* _Harvey P. Dale_, Mar 26 2023 *)
%o A254429 (Haskell)
%o A254429 a254429 n = a254429_list !! n
%o A254429 a254429_list = iterate ((+ 1) . (2 ^)) 0
%o A254429 -- _Reinhard Zumkeller_, Jan 31 2015
%o A254429 (Magma) [n le 2 select 2*(n-1) else 2^Self(n-1)+1: n in [1..5]]; // _Vincenzo Librandi_, Feb 01 2015
%Y A254429 Cf. A007013, A254411.
%Y A254429 Cf. A000051.
%K A254429 nonn
%O A254429 0,2
%A A254429 _Max Alekseyev_, Jan 30 2015