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 A127513 #12 May 21 2020 10:57:44
%S A127513 1,-1,-5,-5,-21,11,-53,-53,-53,459,-565,-565,-4661,3531,19915,19915,
%T A127513 -45621,-45621,-307765,-307765,740811,2837963,-1356341,-1356341,
%U A127513 -1356341,32198091,32198091,32198091,-236237365,-773108277
%N A127513 Partial sums of A127511.
%H A127513 Alois P. Heinz, <a href="/A127513/b127513.txt">Table of n, a(n) for n = 1..1000</a>
%e A127513 a(3) = -5 = (1 - 2 - 4).
%p A127513 a:= proc(n) option remember;
%p A127513 numtheory[mobius](n)*2^(n-1) +`if`(n=1, 0, a(n-1))
%p A127513 end:
%p A127513 seq(a(n), n=1..30); # _Alois P. Heinz_, Apr 04 2012
%t A127513 Table[2^(n-1) MoebiusMu[n], {n, 1, 30}] // Accumulate (* _Jean-François Alcover_, May 21 2020 *)
%Y A127513 Cf. A127511, A127512.
%K A127513 sign
%O A127513 1,3
%A A127513 _Gary W. Adamson_, Jan 17 2007
%E A127513 More terms from _R. J. Mathar_, Apr 04 2012