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 A162599 #19 Jun 16 2024 16:42:57
%S A162599 2,2,3,6,11,26,56,97,204,415,769,1606,3268,6460,12889,25915,52046,
%T A162599 104099,207000,416542,831430,1662247,3324374,6646337,13292865,
%U A162599 26593542,53182276,106364450,212732814,425465107,850887793,1701801109
%N A162599 Sum of digits (bits) in base two representation of 3^(2^n).
%e A162599 3^(2^2) = 81 = 64 + 16 + 1, so a(2) = 3.
%p A162599 a := proc (n) local b2: b2 := convert(3^(2^n), base, 2): add(b2[j], j = 1 .. nops(b2)) end proc: seq(a(n), n = 0 .. 20); # _Emeric Deutsch_, Jul 21 2009
%t A162599 Table[Total[IntegerDigits[3^2^n,2]],{n,0,25}] (* The program generates the first 26 terms of the seequence. *) (* _Harvey P. Dale_, Jun 16 2024 *)
%o A162599 (J, version 6.0.1)
%o A162599 s=:(+/@|:@#:@ (3x ^ 2x ^ i.))
%o A162599 s 13
%o A162599 (PARI) a(n) = hammingweight(3^(2^n)); \\ _Michel Marcus_, Mar 03 2019
%Y A162599 Cf. A000120, A011764 (3^2^n).
%K A162599 nonn,base
%O A162599 0,1
%A A162599 _Daniel R. L. Brown_, Jul 07 2009
%E A162599 Extended by _Emeric Deutsch_, Jul 21 2009
%E A162599 More terms from _Michel Marcus_, Mar 03 2019