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%I #4 Aug 24 2021 09:00:13
%S 1,1,2,1,2,1,2,4,1,2,1,2,3,6,1,2,4,1,2,3,6,1,2,4,6,1,2,5,10,1,2,4,1,2,
%T 3,4,6,12,1,2,3,6,1,2,4,1,2,4,8,1,2,4,8,16,1,2,3,6,1,2,3,6,9,18,1,2,4,
%U 8,12,1,2,3,6,8,1,2,5,6,10,1,2,11,22,1,2,4,8
%N Irregular triangle whose n-th row lists the integers m such that the n-th necklace polynomial is divisible by the m-th cyclotomic polynomial.
%H Trevor Hyde, <a href="https://arxiv.org/abs/1811.08601">Cyclotomic factors of necklace polynomials</a>, arXiv:1811.08601 [math.CO], 2018.
%e Triangle begins:
%e [1]
%e [1, 2]
%e [1, 2]
%e [1, 2, 4]
%e [1, 2]
%e [1, 2, 3, 6]
%e [1, 2, 4]
%e [1, 2, 3, 6]
%e [1, 2, 4, 6]
%e [1, 2, 5, 10]
%e [1, 2, 4]
%e ...
%o (PARI) M(n) = sumdiv(n, d, moebius(d)*x^(n/d));
%o row(n) = my(list=List(), pol=M(n)); for (k=1, n, if (type(pol/polcyclo(k)) == "t_POL", listput(list, k))); Vec(list);
%Y Cf. A013595, A054525, A347223.
%K nonn,tabf
%O 2,3
%A _Michel Marcus_, Aug 24 2021
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