cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-7 of 7 results.

A278571 Index of first occurrence of n in A278567.

Original entry on oeis.org

1, 7, 42, 385, 436, 1530, 3180, 3625, 8208, 3767, 10116, 6699
Offset: 1

Views

Author

N. J. A. Sloane, Nov 27 2016

Keywords

Crossrefs

Cf. A278567.

Extensions

a(12) corrected by Don Reble, Nov 27 2016

A013595 Irregular triangle read by rows: coefficients of cyclotomic polynomial Phi_n(x) (exponents in increasing order).

Original entry on oeis.org

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
Offset: 0

Views

Author

Keywords

Comments

We follow Maple in defining Phi_0 to be x; it could equally well be taken to be 1.
From Wolfdieter Lang, Oct 29 2013: (Start)
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

Examples

			Phi_0 = x; Phi_1 = x - 1; Phi_2 = x + 1; Phi_3 = x^2 + x + 1; Phi_4 = x^2 + 1; ...
From _Wolfdieter Lang_, Oct 29 2013: (Start)
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)
		

References

  • 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.

Crossrefs

Cf. A013596, A020500 (row sums, n >= 1), A020513 (alternating row sums).
For record coefficients see A160340, A262404, A262405, A278567.
Column m=1 is A157657.

Programs

  • Maple
    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]
    # Robert Israel, Apr 17 2014
  • Mathematica
    Table[CoefficientList[x^KroneckerDelta[n] Cyclotomic[n, x], x], {n, 0, 15}] // Flatten (* Peter Luschny, Dec 27 2016 *)
  • PARI
    row(n) = if (n==0, p=x, p = polcyclo(n)); Vecrev(p); \\ Michel Marcus, Dec 14 2015

Formula

a(n,m) = [x^m] Phi_n(x), n >= 0, 0 <= m <= phi(n), with phi(n) = A000010(n). - Wolfdieter Lang, Oct 29 2013

Extensions

Maple program corrected by Robert Israel, Apr 17 2014

A160340 Indices of records in heights of cyclotomic polynomials (A160338).

Original entry on oeis.org

1, 105, 385, 1365, 1785, 2805, 3135, 6545, 10465, 11305, 17255, 20615, 26565, 40755, 106743, 171717, 255255, 279565, 327845, 707455, 886445, 983535, 1181895, 1752465, 3949491, 8070699, 10163195, 13441645, 15069565, 30489585, 37495115, 40324935
Offset: 1

Views

Author

Max Alekseyev, May 13 2009

Keywords

Comments

m is in this sequence if A160338(k) < A160338(m) for all k

Crossrefs

Subsequence of A013594 and A046887.

Programs

  • Mathematica
    r = 0; Do[If[# > r, r = #; Print[n]] &@ Max@ Abs@ CoefficientList[Cyclotomic[n, x], x], {n, 10^4}] (* Michael De Vlieger, May 20 2024 *)
  • PARI
    print1(r=1); for(n=2,1e4, t=vecmax(abs(Vec(polcyclo(n)))); if(t>r, r=t; print1(", "n))) \\ Charles R Greathouse IV, Jun 28 2012

A262404 Least k such that the k-th cyclotomic polynomial has n as a coefficient.

Original entry on oeis.org

4, 1, 165, 595, 1785, 1785, 2805, 3135, 6545, 6545, 10465, 10465, 10465, 10465, 10465, 11305, 11305, 11305, 11305, 11305, 11305, 11305, 15015, 11305, 20615, 17255, 20615, 20615, 26565, 26565, 26565, 26565, 26565, 26565, 26565, 26565, 26565, 26565, 26565, 26565, 26565
Offset: 0

Author

Keywords

Comments

Suzuki proves that a(n) exists for each n. Vaughan proves that there are infinitely many k with a(n) = k and n > exp(exp(log 2 * log k/log log k)).

Examples

			Phi(165) = x^80 + x^79 + x^78 - x^75 - x^74 - x^73 - x^69 - x^68 - x^67 + x^65 + 2x^64 + 2x^63 + x^62 - x^60 - x^59 - x^58 - x^54 - x^53 - x^52 + x^50 + 2x^49 + 2x^48 + 2x^47 + x^46 - x^44 - x^43 - x^42 - x^41 - x^40 - x^39 - x^38 - x^37 - x^36 + x^34 + 2x^33 + 2x^32 + 2x^31 + x^30 - x^28 - x^27 - x^26 - x^22 - x^21 - x^20 + x^18 + 2x^17 + 2x^16 + x^15 - x^13 - x^12 - x^11 - x^7 - x^6 - x^5 + x^2 + x + 1, with 2 as the coefficient of x^16 (among others), and this is the least k for which 2 appears, so a(2) = 165.
		

Programs

  • Maple
    N:= 40: count:= 0: A:= Array(0..N): A[0]:= 4:
    for k from 1 while count < N do
      S:= select(t -> t::posint and t <= N and A[t] = 0, {coeffs(numtheory:-cyclotomic(k,x),x)}):
      if S <> {} then
        A[convert(S,list)]:= k;
        count:= count + nops(S);
      fi
    od:
    convert(A,list); # Robert Israel, Dec 23 2018
  • Mathematica
    Table[k = 1; While[! MemberQ[CoefficientList[Cyclotomic[k, x], x], n], k++]; k, {n, 0, 9}] (* Michael De Vlieger, Sep 29 2015 *)
  • PARI
    a(n)=my(k,v);while(!setsearch(Set(Vec(polcyclo(k++))),n),);k

Extensions

Corrected a(22); more terms from Seiichi Manyama, Dec 22 2018

A262405 Least k such that the k-th cyclotomic polynomial has -n as a coefficient.

Original entry on oeis.org

4, 1, 105, 385, 1365, 2145, 2805, 3135, 6545, 7917, 10465, 10465, 10465, 10465, 10465, 11305, 11305, 11305, 11305, 11305, 11305, 11305, 15015, 17255, 17255, 17255, 20615, 25935, 26565, 26565, 26565, 26565, 26565, 26565, 26565, 26565, 26565, 26565, 26565, 26565, 26565, 26565
Offset: 0

Author

Keywords

Comments

Suzuki proves that a(n) exists for each n.

Examples

			Phi(105) = x^48 + x^47 + x^46 - x^43 - x^42 - 2x^41 - x^40 - x^39 + x^36 + x^35 + x^34 + x^33 + x^32 + x^31 - x^28 - x^26 - x^24 - x^22 - x^20 + x^17 + x^16 + x^15 + x^14 + x^13 + x^12 - x^9 - x^8 - 2x^7 - x^6 - x^5 + x^2 + x + 1, with -2 as the coefficient of x^7 (among others), and this is the least k for which -2 appears, so a(2) = 105.
		

Programs

  • Mathematica
    Table[k = 1; While[! MemberQ[CoefficientList[Cyclotomic[k, x], x], -n], k++]; k, {n, 0, 9}] (* Michael De Vlieger, Sep 29 2015 *)
  • PARI
    a(n)=my(k,v);while(!setsearch(Set(Vec(polcyclo(k++))),-n),);k

Extensions

More terms from Seiichi Manyama, Dec 22 2018

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).

Original entry on oeis.org

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
Offset: 1

Author

N. J. A. Sloane, Nov 27 2016

Keywords

References

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

Crossrefs

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

Programs

  • 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 *)

A373196 Maximal coefficient (in absolute value) in the numerator of C({1..n},x).

Original entry on oeis.org

1, 1, 2, 17, 444, 66559954, 14648786369948422, 791540878703169050660325841979096789557779, 1918013047695258943191946313451491492494186620117241479813740479213857275772347178176158
Offset: 0

Author

John Tyler Rascoe, Jun 28 2024

Keywords

Examples

			C_x({1,2,3},x) = (-x^15 - 5*x^14 - 12*x^13 - 17*x^12 - 11*x^11 + 4*x^10 + 16*x^9 + 10*x^8 - 6*x^6)/(x^15 + 4*x^14 + 7*x^13 + 4*x^12 - 8*x^11 - 18*x^10 - 13*x^9 + 7*x^8 + 19*x^7 + 11*x^6 - 6*x^5 - 10*x^4 - 2*x^3 + 3*x^2 + 2*x - 1) with maximal coefficient abs(-17) in the numerator, so a(3) = 17.
		

Crossrefs

Programs

  • PARI
    C_x(s)={my(g=if(#s <1,1, sum(i=1,#s, C_x(s[^i])*x^(s[i]))/(1-sum(i=1,#s, x^(s[i]))))); return(g)}
    a(n)={vecmax(abs(Vec(numerator(C_x([1..n])))))}

Formula

C({s},x) = Sum_{i in {s}} (C({s}-{i},x)*x^i)/(1 - Sum_{i in {s}} (x^i)) with C({},x) = 1.
Showing 1-7 of 7 results.