A278570 - OEIS

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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).

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, 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, 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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

REFERENCES

Don Reble, Posting to Sequence Fans Mailing List, Nov 26 2016

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..20000

MAPLE

with(numtheory):

b:= proc(n) option remember; local k;

for k from 2+`if`(n=1, 1, b(n-1)) by 2 while

bigomega(k)<>3 or nops(factorset(k))<>3 do od; k

end:

a:= n-> max(map(abs, [coeffs(cyclotomic(b(n), x))])):

seq(a(n), n=1..120); # Alois P. Heinz, Nov 27 2016

MATHEMATICA

b[n_] := b[n] = (For[k = 2 + If[n == 1, 1, b[n-1]], PrimeOmega[k] != 3 || PrimeNu[k] != 3, k += 2]; k);

a[n_] := Max @ Abs @ CoefficientList[Cyclotomic[b[n], x], x];

Array[a, 120] (* Jean-François Alcover, Mar 28 2017, after Alois P. Heinz *)

CROSSREFS

Cf. A046389. See A278567 for a closely related sequence.

Sequence in context: A129139 A032539 A122922 * A046799 A348172 A319506

Adjacent sequences: A278567 A278568 A278569 * A278571 A278572 A278573

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Nov 27 2016

STATUS

approved