A382653 -id:A382653 - cp's OEIS frontend

A382670 Numbers k such that a regular k-gon (k>=3) can be constructed with a compass, straightedge and an angle quinsector.

3, 4, 5, 6, 8, 10, 11, 12, 15, 16, 17, 20, 22, 24, 25, 30, 32, 33, 34, 40, 41, 44, 48, 50, 51, 55, 60, 64, 66, 68, 75, 80, 82, 85, 88, 96, 100, 101, 102, 110, 120, 123, 125, 128, 132, 136, 150, 160, 164, 165, 170, 176, 187, 192, 200, 202, 204, 205, 220, 240

Offset: 1

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Chai Wah Wu, Apr 02 2025

nonn

Andrew M. Gleason, Angle Trisection, the Heptagon and the Triskaidecagon, American Mathematical Monthly, 95 (1988), 185-194.

Cf. A048135, A048136, A382653.

from itertools import count, islice
from sympy import primefactors, totient
def A382670_gen(): # generator of terms
    yield from filter(lambda n: set(primefactors(totient(n))) <= {2,5}, count(3))
A382670_list = list(islice(A382670_gen(),70))

cp's OEIS Frontend

A382670 Numbers k such that a regular k-gon (k>=3) can be constructed with a compass, straightedge and an angle quinsector.

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