A230798 - OEIS

%I #15 Mar 13 2015 23:50:30

%S 2,1,1,2,1,2,1,2,2,2,1,3,1,2,3,2,1,3,1,3,3,2,1,3,2,2,2,3,1,3,1,2,3,2,

%T 3,3,1,2,3,3,1,3,1,3,3,2,1,3,2,3,3,3,1,3,3,3,3,2,1,3,1,2,3,2,3,3,1,3,

%U 3,3,1,3,1,2,3,3,3,3,1,3,2,2,1,3,3,2

%N The number of distinct coefficients in the n-th cyclotomic polynomial.

%C a(n) = 1 if n is a prime.

%C The sum of the coefficients in the n-th cyclotomic polynomial is given by A020500.

%C The first occurrence of 4 in this sequence is a(105).

%H T. D. Noe, <a href="/A230798/b230798.txt">Table of n, a(n) for n = 1..10000</a>

%e a(12)=3 because the distinct coefficients of the 12th cyclotomic polynomial, x^4-x^2+1, are 0, 1 and -1.

%t Table[Length[Union[CoefficientList[Cyclotomic[n, x], x]]], {n, 100}] (* _T. D. Noe_, Dec 09 2013 *)

%o (PARI) a(n) = #vecsort(Vec(polcyclo(n)),,8)

%Y Cf. A020500, A230799.

%Y Cf. A231611 (least k for which cyclotomic(k) has n distinct terms).

%K nonn

%O 1,1

%A _Colin Barker_, Oct 30 2013