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 A105608 #14 Jun 06 2025 08:06:01
%S A105608 1,1,1,2,1,12,1,16,6,88,1,960,1,656,264,896,1,48960,1,53504,1968,
%T A105608 36544,1,2795520,44,272768,2448,2980864,1,1547335680,1,2781184,109632,
%U A105608 15196672,14432,8635760640,1,113429504,818304,8677064704,1,4808968273920,1,9252356096,415337472,6319476736,1,26795484119040,328,3584860454912
%N A105608 Sylvester dividends for A002605.
%H A105608 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SylvesterCyclotomicNumber.html">Sylvester Cyclotomic Number</a>.
%F A105608 a(n) = A002605(n)/A105607(n); a(n) = Product_{k=1..n-1, gcd(n, k)>1} (1+sqrt(3))-(1-sqrt(3))*exp(2*Pi*i*k/n), i = sqrt(-1).
%t A105608 f[n_] := FullSimplify[ Expand[ Times @@ ((1+Sqrt[3])-(1-Sqrt[3])*Exp[2Pi*I*Select[Range[n-1], GCD[ #, n] > 1 &]/n])]]; Table[ f[n], {n, 1, 32}] (* _Robert G. Wilson v_, Aug 02 2005 *)
%Y A105608 Cf. A105607, A105609.
%K A105608 easy,nonn
%O A105608 1,4
%A A105608 _Paul Barry_, Apr 15 2005
%E A105608 More terms from _David Wasserman_, May 06 2008