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 A066538 #36 Oct 16 2024 09:19:27
%S A066538 3,7,4,10,19,13,28,46,73,112,139,154,697,847,1675,3106,3106,4258,5755,
%T A066538 5950,13216,13693,14980,27202,28939,31339,60337,116455,149365,179488,
%U A066538 291745,1026544,1163443,1704376,1893388,4038358,4092673,9440671,18243946,28445131,32580433,35170384,41201947,44142151,50349694,57766339,58416637
%N A066538 Sum of the digits of the n-th Mersenne prime (A000668).
%C A066538 From _Gord Palameta_, Jul 21 2018: (Start)
%C A066538 a(38) and a(39) were calculated by _Enoch Haga_, Sep 07 1999 and Dec 17 2001; a(40) through a(42) were calculated by _Andrew Rupinski_, Mar 12 2005. (See the Carlos Rivera link.)
%C A066538 It appears that asymptotically a(n)/A000043(n) = 9*log_10(2)/2. (End)
%H A066538 Amiram Eldar, <a href="/A066538/b066538.txt">Table of n, a(n) for n = 1..48</a> (terms 1..47 from Gord Palameta)
%H A066538 Carlos Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_074.htm">Puzzle 74.- SOD(2^6972593-1)</a>, The Prime Puzzles & Problems Connection.
%F A066538 a(n) = A007953(A000668(n)). - _Amiram Eldar_, Oct 16 2024
%t A066538 ep = {the exponents from A000043}; a = {}; Do[ a = Append[a, Apply[ Plus, IntegerDigits[ 2^ep[[n]] - 1]]], {n, 1, 47} ]; a
%t A066538 (* Second program: *)
%t A066538 Array[Total@ IntegerDigits[2^MersennePrimeExponent@ # - 1] &, 45] (* _Michael De Vlieger_, Jul 22 2018 *)
%Y A066538 Cf. A000043, A000668, A007953, A001348.
%Y A066538 Subsequence of: A007953, A007605.
%Y A066538 Cf. A001370 (sum of digits of 2^n).
%K A066538 base,nonn
%O A066538 1,1
%A A066538 _Robert G. Wilson v_, Jan 06 2002
%E A066538 Definition corrected by _Omar E. Pol_, Apr 01 2008
%E A066538 a(38)-a(47) from _Gord Palameta_, Jul 21 2018