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A013595
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Irregular triangle read by rows: coefficients of cyclotomic polynomial Phi_n(x) (exponents in increasing order).
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33
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0, 1, -1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, -1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, -1, 1, -1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, -1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, -1, 1, -1, 1, -1, 1, 1, -1, 0, 1, -1, 1, 0, -1, 1
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OFFSET
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0,3440
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COMMENTS
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We follow Maple in defining Phi_0 to be x; it could equally well be taken to be 1.
The length of row n >= 1 of this table is phi(n) + 1 = A000010(n) + 1. Row n = 0 has here length 2.
Phi_n(x) is the minimal polynomial of omega_n := exp(i*2*Pi/n) over the rationals. Namely, Phi_n(x) = Product_{k=0..n-1, gcd(k,n)=1} (x - (omega_n)^k). See the Graham et al. reference, 4.50 a, pp. 149, 506.
Phi_n(x) = Product_{d|n} (x^d - 1)^(mu(n/d)) with the Moebius function mu(n) = A008683(n), n >= 1. See the Graham et al. reference, 4.50 b, pp. 149, 506.
Phi_n(x) = Phi_{rad(n)}(x^(n/rad(n))), n >= 2, with rad(n) = A007947(n), the squarefree kernel of n. Proof from the preceding formula, where only squarefree n/d (A005117) from the set of divisors of n enter, by mapping each factor (numerator or denominator) of the left hand side to one of the right hand side and vice versa.
(End)
Each row can be considered as the last column of the companion matrix of the cyclotomic polynomial: A000010(n) is the size of such a square matrix, last column has opposite signs and the last term (before last term of each row in A013595) equal to A008683(n). - Eric Desbiaux, Dec 14 2015
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REFERENCES
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E. R. Berlekamp, Algebraic Coding Theory, McGraw-Hill, 1968; see p. 90.
Z. I. Borevich and I. R. Shafarevich, Number Theory. Academic Press, NY, 1966, p. 325.
R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics, Addison-Wesley, 1991, p. 137.
K. Ireland and M. Rosen, A Classical Introduction to Modern Number Theory, Springer, 1982, p. 194.
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LINKS
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FORMULA
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EXAMPLE
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Phi_0 = x; Phi_1 = x - 1; Phi_2 = x + 1; Phi_3 = x^2 + x + 1; Phi_4 = x^2 + 1; ...
The irregular triangle a(n,m) begins:
n\m 0 1 2 3 4 5 6 7 8 9 10 11 12 ...
0: 0 1
1: -1 1
2: 1 1
3: 1 1 1
4: 1 0 1
5: 1 1 1 1 1
6: 1 -1 1
7: 1 1 1 1 1 1 1
8: 1 0 0 0 1
9: 1 0 0 1 0 0 1
10: 1 -1 1 -1 1
11: 1 1 1 1 1 1 1 1 1 1 1
12: 1 0 -1 0 1
13: 1 1 1 1 1 1 1 1 1 1 1 1 1
14: 1 -1 1 -1 1 -1 1
15: 1 -1 0 1 -1 1 0 -1 1
...
Phi_15(x) = (x^1 - 1)*((x^3 - 1)^(-1))*((x^5 - 1)^(-1))*(x^15 - 1) because mu(15) = mu(1) = +1 and mu(3) = mu(5) = -1. Hence Phi_15(x) = 1 - x + x^3 - x^4 + x^5 - x^7 + x^8, giving row n = 15.
Example for the reduction via the squarefree kernel: Phi_12(x) = Phi_6(x^(12/6)) = Phi_6(x^2). By the formula with the Mobius function Phi_6(x) = Phi_2(x^3)/Phi_2(x) = 1 - x + x^2 and with x -> x^2 this becomes Phi_12(x) = 1 - x^2 + x^4.
(End)
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MAPLE
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N:= 100: # to get coefficients up to cyclotomic(N, x)
with(numtheory):
for n from 0 to N do
C:= cyclotomic(n, x);
L[n]:= seq(coeff(C, x, i), i=0..degree(C));
od:
A:= [seq](L[n], n=0..N): # note that A013595(n) = A[n+1]
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MATHEMATICA
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Table[CoefficientList[x^KroneckerDelta[n] Cyclotomic[n, x], x], {n, 0, 15}] // Flatten (* Peter Luschny, Dec 27 2016 *)
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PROG
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(PARI) row(n) = if (n==0, p=x, p = polcyclo(n)); Vecrev(p); \\ Michel Marcus, Dec 14 2015
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CROSSREFS
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KEYWORD
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sign,easy,nice,tabf
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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