cp's OEIS Frontend

A278570 a(n) = maximum absolute value of coefficients in the cyclotomic polynomial C(N,x), where N = n-th number which a product of three distinct odd primes = A046389(n).

%I A278570 #18 Oct 19 2017 10:46:18
%S A278570 2,2,2,1,2,2,2,2,2,3,1,2,1,2,1,1,2,2,3,2,2,2,2,1,1,3,2,2,1,2,2,2,2,1,
%T A278570 1,2,1,1,3,2,2,2,2,2,2,2,2,2,2,2,2,1,2,1,2,1,2,3,2,2,2,1,2,3,1,1,1,2,
%U A278570 2,2,1,2,3,1,2,3,2,2,1,2,2,2,1,2,1,2,2,2,2,1,2,2,2,2,3,1,2,2,2,1,3,2
%N A278570 a(n) = maximum absolute value of coefficients in the cyclotomic polynomial C(N,x), where N = n-th number which a product of three distinct odd primes = A046389(n).
%D A278570 _Don Reble_, Posting to Sequence Fans Mailing List, Nov 26 2016
%H A278570 Alois P. Heinz, <a href="/A278570/b278570.txt">Table of n, a(n) for n = 1..20000</a>
%p A278570 with(numtheory):
%p A278570 b:= proc(n) option remember; local k;
%p A278570       for k from 2+`if`(n=1, 1, b(n-1)) by 2 while
%p A278570       bigomega(k)<>3 or nops(factorset(k))<>3 do od; k
%p A278570     end:
%p A278570 a:= n-> max(map(abs, [coeffs(cyclotomic(b(n), x))])):
%p A278570 seq(a(n), n=1..120);  # _Alois P. Heinz_, Nov 27 2016
%t A278570 b[n_] := b[n] = (For[k = 2 + If[n == 1, 1, b[n-1]], PrimeOmega[k] != 3 || PrimeNu[k] != 3, k += 2]; k);
%t A278570 a[n_] :=  Max @ Abs @ CoefficientList[Cyclotomic[b[n], x], x];
%t A278570 Array[a, 120] (* _Jean-François Alcover_, Mar 28 2017, after _Alois P. Heinz_ *)
%Y A278570 Cf. A046389. See A278567 for a closely related sequence.
%K A278570 nonn
%O A278570 1,1
%A A278570 _N. J. A. Sloane_, Nov 27 2016