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A107067 Number of polynomials with coefficients in {0,1} and which divide x^n-1. 3
1, 2, 2, 4, 2, 6, 2, 8, 4, 6, 2, 17, 2, 6, 6, 16, 2, 18, 2, 17, 6, 6, 2, 48, 4, 6, 8, 17, 2, 36, 2, 32, 6, 6, 6, 69, 2, 6, 6, 47, 2, 36, 2, 17, 17, 6, 2, 136, 4, 18, 6, 17, 2, 54, 6, 47, 6, 6, 2, 176, 2, 6, 17, 64, 6, 36, 2, 17, 6, 36, 2, 257, 2, 6, 18, 17, 6, 36, 2, 131, 16, 6, 2, 177, 6, 6, 6, 47, 2, 183, 6, 17, 6, 6, 6, 389, 2, 18, 17, 70, 2, 36, 2, 47, 35 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

From Robert Israel, May 22 2017:

Each of these polynomials is a product of distinct cyclotomic polynomials C_k(x) for k > 1 dividing n.

a(n) <= 2^(A000005(n)-1).

If n is prime then a(n) = 2. (End)

LINKS

Robert Israel, Table of n, a(n) for n = 1..719(first 359 terms from Antti Karttunen)

MAPLE

f:= proc(n) local t, C, x, S;

  C:= map(m -> numtheory:-cyclotomic(m, x), numtheory:-divisors(n) minus {1});

  t:= 0:

  S:= combinat:-subsets(C);

  while not S[finished] do

  if {coeffs(expand(convert(S[nextvalue](), `*`)), x)} = {1} then

    t:= t+1;

  fi

od;

t

end proc:

map(f, [$1..100]); # Robert Israel, May 22 2017

PROG

(PARI) for(n=1, 100, m=0; p=x^n-1; nE=numdiv(n); P=factor(p); E=P[, 2]; P=P[, 1]; forvec(v=vector(nE, i, [0, E[i]]), divp=prod(k=1, nE, P[k]^v[k]); m++; for(j=0, poldegree(divp), divpcof=polcoeff(divp, j); if(divpcof<0 || divpcof>1, m--; break))); print1(m, ", ")) // Herman Jamke (hermanjamke(AT)fastmail.fm), Nov 15 2006

CROSSREFS

Cf. A107336, A107748.

Sequence in context: A278237 A328707 A067824 * A331580 A320389 A046801

Adjacent sequences:  A107064 A107065 A107066 * A107068 A107069 A107070

KEYWORD

nonn

AUTHOR

Ralf Stephan, following a suggestion from Max Alekseyev, Jun 11 2005

EXTENSIONS

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Nov 15 2006

Data section further extended and b-file computed with Jamke's PARI-program by Antti Karttunen, May 22 2017

STATUS

approved

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Last modified August 8 06:27 EDT 2020. Contains 336290 sequences. (Running on oeis4.)