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 A382670 #15 Apr 03 2025 14:57:38
%S A382670 3,4,5,6,8,10,11,12,15,16,17,20,22,24,25,30,32,33,34,40,41,44,48,50,
%T A382670 51,55,60,64,66,68,75,80,82,85,88,96,100,101,102,110,120,123,125,128,
%U A382670 132,136,150,160,164,165,170,176,187,192,200,202,204,205,220,240
%N A382670 Numbers k such that a regular k-gon (k>=3) can be constructed with a compass, straightedge and an angle quinsector.
%H A382670 Andrew M. Gleason, <a href="http://www.jstor.org/stable/2323624">Angle Trisection, the Heptagon and the Triskaidecagon</a>, American Mathematical Monthly, 95 (1988), 185-194.
%o A382670 (Python)
%o A382670 from itertools import count, islice
%o A382670 from sympy import primefactors, totient
%o A382670 def A382670_gen(): # generator of terms
%o A382670 yield from filter(lambda n: set(primefactors(totient(n))) <= {2,5}, count(3))
%o A382670 A382670_list = list(islice(A382670_gen(),70))
%Y A382670 Cf. A048135, A048136, A382653.
%K A382670 nonn
%O A382670 1,1
%A A382670 _Chai Wah Wu_, Apr 02 2025