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 A295505 #28 Dec 11 2020 03:56:43
%S A295505 1,3,15,60,255,1005,4095,16320,65520,261885,1048575,4193220,16777215,
%T A295505 67104765,268435185,1073725440,4294967295,17179802640,68719476735,
%U A295505 274877644740,1099511623665,4398045462525,17592186044415,70368739967040,281474976710400
%N A295505 a(n) = Sum_{d|n} mu(n/d)*4^(d-1).
%H A295505 Seiichi Manyama, <a href="/A295505/b295505.txt">Table of n, a(n) for n = 1..1661</a>
%F A295505 a(n) = A054719(n)/4 for n > 0.
%F A295505 G.f.: Sum_{k>=1} mu(k)*x^k/(1 - 4*x^k). - _Ilya Gutkovskiy_, Oct 25 2018
%t A295505 Table[Sum[MoebiusMu[n/d]4^(d-1),{d,Divisors[n]}],{n,30}] (* _Harvey P. Dale_, Nov 08 2020 *)
%t A295505 nmax = 20; Rest[CoefficientList[Series[Sum[MoebiusMu[k] * x^k / (1 - 4*x^k), {k, 1, nmax}], {x, 0, nmax}], x]] (* _Vaclav Kotesovec_, Dec 11 2020 *)
%o A295505 (PARI) {a(n) = sumdiv(n, d, moebius(n/d)*4^(d-1))}
%Y A295505 Sum_{d|n} mu(n/d)*k^(d-1): A000740 (k=2), A034741 (k=3), this sequence (k=4), A295506 (k=5).
%Y A295505 Column k=4 of A143325.
%Y A295505 First differences of A320088.
%Y A295505 Cf. A054719.
%K A295505 nonn
%O A295505 1,2
%A A295505 _Seiichi Manyama_, Nov 23 2017