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 A229727 #6 Jun 28 2021 19:16:03
%S A229727 2,20,256,4832,42496,1467392,62836736,42790912,2535587840,
%T A229727 170851041280,3070050172928,256460544016384,4697678227177472,
%U A229727 52001663422038016,5598478396465086464,647670579588837146624,2427980359983876276224,9138219784535816536064,1277040945143933271277568
%N A229727 Numerator of Sum_{k=1..2n+1} 2^k/k.
%e A229727 2, 20/3, 256/15, 4832/105, 42496/315, 1467392/3465, 62836736/45045, 42790912/9009, 2535587840/153153, 170851041280/2909907, 3070050172928/14549535, 256460544016384/334639305, 4697678227177472/1673196525, 52001663422038016/5019589575, ...
%t A229727 Take[Numerator[Accumulate[Table[2^k/k,{k,51}]]],{1,-1,2}] (* _Harvey P. Dale_, Jun 28 2021 *)
%Y A229727 Cf. A229726, A108866.
%K A229727 nonn,frac
%O A229727 0,1
%A A229727 _N. J. A. Sloane_, Sep 28 2013