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 A045665 #12 Oct 02 2019 20:05:13
%S A045665 1,2,4,6,16,30,36,98,128,252,300,682,720,1638,1764,3690,4096,8670,
%T A045665 9072,19418,20400,42630,45012,94162,97920,204600,212940,441504,458640,
%U A045665 950214,981900,2031554,2097152,4323198,4456380,9174270,9434880
%N A045665 Number of 2n-bead balanced binary strings of fundamental period 2n, rotationally equivalent to reverse, complement and reversed complement.
%H A045665 Andrew Howroyd, <a href="/A045665/b045665.txt">Table of n, a(n) for n = 0..1000</a>
%F A045665 a(n) = 2*n*A045683(n) for n > 0.
%F A045665 a(n) = n * Sum_{d|n, d odd} mu(d) * 2^ceiling(n/(2*d)) for n > 0.
%o A045665 (PARI) a(n)={if(n<1, n==0, n*sumdiv(n, d, if(d%2, moebius(d)*2^((n/d+1)\2))))} \\ _Andrew Howroyd_, Oct 01 2019
%Y A045665 Cf. A007727, A045662, A045663, A045664, A045674, A045683.
%K A045665 nonn
%O A045665 0,2
%A A045665 _David W. Wilson_