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 1-9 of 9 results.

A059913 Triangle T(n,k) of numbers of n degree irreducible polynomials over GF(2) which have order A059912(n,k), k=1..A059499(n).

Original entry on oeis.org

2, 1, 2, 1, 2, 6, 1, 2, 6, 18, 2, 4, 8, 16, 8, 48, 1, 2, 6, 30, 60, 2, 8, 176, 1, 2, 2, 2, 4, 6, 4, 6, 8, 12, 12, 24, 24, 36, 48, 144, 630, 3, 6, 18, 378, 756, 10, 12, 60, 300, 1800, 16, 32, 64, 128, 256, 512, 1024, 2048, 7710, 1, 1, 2, 6, 6, 6, 8, 12, 18, 24
Offset: 1

Views

Author

Vladeta Jovovic, Feb 09 2001

Keywords

Comments

Row sums give A001037.

Examples

			There are 9 (cf. A001037) irreducible polynomials of degree 6 over GF(2): 1 of order 9, 2 of order 21 and 6 of order 63 (cf. A059912).
Triangle T(n,k) begins:
  2;
  1;
  2;
  1,  2;
  6;
  1,  2,   6;
  18;
  2,  4,   8, 16;
  8, 48;
  1,  2,   6, 30, 60;
  2,  8, 176;
  ...
		

Crossrefs

Programs

  • Mathematica
    Prepend[Table[Map[EulerPhi[#]/n &, Complement[Divisors[2^n - 1],Union[Flatten[Table[Divisors[2^k - 1], {k, 1, n - 1}]]]]], {n, 2,20}], {2}] // Grid (* Geoffrey Critzer, Dec 02 2019 *)

Formula

T(n,k) = phi(A059912(n,k))/n, where phi = Euler totient function A000010.

A059499 a(n) = |{m : multiplicative order of 2 mod m = n}|.

Original entry on oeis.org

1, 1, 1, 2, 1, 3, 1, 4, 2, 5, 3, 16, 1, 5, 5, 8, 1, 24, 1, 38, 9, 11, 3, 68, 6, 5, 4, 54, 7, 79, 1, 16, 11, 5, 13, 462, 3, 5, 13, 140, 3, 123, 7, 110, 54, 11, 7, 664, 2, 114, 29, 118, 7, 124, 59, 188, 13, 55, 3, 4456, 1, 5, 82, 96, 5, 353, 3, 118, 11, 485, 7
Offset: 1

Views

Author

Vladeta Jovovic, Feb 04 2001

Keywords

Comments

Also, number of primitive factors of 2^n - 1 (cf. A212953). - Max Alekseyev, May 03 2022
The multiplicative order of a mod m, gcd(a,m)=1, is the smallest natural number d for which a^d = 1 (mod m). See A002326.
a(n) is odd iff n is squarefree, A005117. - Thomas Ordowski, Jan 18 2014
The set S for which a(n) = |S| contains an odd number of prime powers p^k, where k > 0 and p == 3 (mod 4), iff n is squarefree and greater than one. - Isaac Saffold, Dec 28 2019

Examples

			a(3) = |{7}| = 1, a(4) = |{5,15}| = 2, a(6) = |{9,21,63}| = 3.
		

Crossrefs

Column k=2 of A212957.
Primitive factors of b^n - 1: this sequence (b=2), A059885 (b=3), A059886 (b=4), A059887 (b=5), A059888 (b=6), A059889 (b=7), A059890 (b=8), A059891 (b=9), A059892 (b=10).

Programs

  • Maple
    with(numtheory):
    a:= n-> add(mobius(n/d)*tau(2^d-1), d=divisors(n)):
    seq(a(n), n=1..100);  # Alois P. Heinz, May 31 2012
  • Mathematica
    a[n_] := Sum[ MoebiusMu[n/d] * DivisorSigma[0, 2^d - 1], {d, Divisors[n]}]; Table[a[n], {n, 1, 71} ] (* Jean-François Alcover, Dec 12 2012 *)
  • PARI
    a(n) = sumdiv(n, d, moebius(n/d) * numdiv(2^d-1)); \\ Amiram Eldar, Jan 25 2025

Formula

a(n) = Sum_{d|n} A008683(n/d) * A046801(d) = Sum_{d|A007947(n)} A008683(d) * A046801(n/d). - Max Alekseyev, May 03 2022
a(n) = 1 iff 2^n-1 is noncomposite. a(prime(n)) = 2^A088863(n)-1. - Thomas Ordowski, Jan 16 2014

Extensions

More terms from John W. Layman, Mar 22 2002
More terms from Alois P. Heinz, May 31 2012

A212737 Square array A(n,k), n>=1, k>=1, read by antidiagonals, where column k lists the orders of degree-d irreducible polynomials over GF(prime(k)); listing order for each column: ascending d, ascending value.

Original entry on oeis.org

1, 1, 3, 1, 2, 7, 1, 2, 4, 5, 1, 2, 4, 8, 15, 1, 2, 3, 3, 13, 31, 1, 2, 5, 6, 6, 26, 9, 1, 2, 3, 10, 4, 8, 5, 21, 1, 2, 4, 4, 3, 8, 12, 10, 63, 1, 2, 3, 8, 6, 4, 12, 24, 16, 127, 1, 2, 11, 6, 16, 12, 6, 16, 31, 20, 17, 1, 2, 4, 22, 9, 3, 7, 8, 24, 62, 40, 51
Offset: 1

Views

Author

Alois P. Heinz, Jun 02 2012

Keywords

Examples

			For k=1 the irreducible polynomials over GF(prime(1)) = GF(2) of degree 1-4 are: x, 1+x; 1+x+x^2; 1+x+x^3, 1+x^2+x^3; 1+x+x^2+x^3+x^4, 1+x+x^4, 1+x^3+x^4. The orders of these polynomials p (i.e., the smallest integer e for which p divides x^e+1) are 1; 3; 7; 5, 15. (Example: (1+x^3+x^4) * (1+x^3+x^4+x^6+x^8+x^9+x^10+x^11) == x^15+1 (mod 2)). Thus column k=1 begins: 1, 3, 7, 5, 15, ... .
Square array A(n,k) begins:
    1,  1,  1,  1,  1,  1,  1,  1,  1,  1, ...
    3,  2,  2,  2,  2,  2,  2,  2,  2,  2, ...
    7,  4,  4,  3,  5,  3,  4,  3, 11,  4, ...
    5,  8,  3,  6, 10,  4,  8,  6, 22,  7, ...
   15, 13,  6,  4,  3,  6, 16,  9,  3, 14, ...
   31, 26,  8,  8,  4, 12,  3, 18,  4, 28, ...
    9,  5, 12, 12,  6,  7,  6,  4,  6,  3, ...
   21, 10, 24, 16,  8,  8,  9,  5,  8,  5, ...
   63, 16, 31, 24, 12, 14, 12,  8, 12,  6, ...
  127, 20, 62, 48, 15, 21, 18, 10, 16,  8, ...
		

Crossrefs

Programs

Formula

Formulae for the column sequences are given in A059912, A212906, ... .

A213224 Minimal order A(n,k) of degree-n irreducible polynomials over GF(prime(k)); square array A(n,k), n>=1, k>=1, read by antidiagonals.

Original entry on oeis.org

1, 1, 3, 1, 4, 7, 1, 3, 13, 5, 1, 4, 31, 5, 31, 1, 3, 9, 13, 11, 9, 1, 7, 7, 5, 11, 7, 127, 1, 3, 9, 16, 2801, 7, 1093, 17, 1, 4, 307, 5, 25, 36, 19531, 32, 73, 1, 3, 27, 5, 30941, 9, 29, 32, 757, 11, 1, 3, 7, 16, 88741, 63, 43, 64, 19, 44, 23
Offset: 1

Views

Author

Alois P. Heinz, Jun 06 2012

Keywords

Comments

Maximal order of degree-n irreducible polynomials over GF(prime(k)) is prime(k)^n-1 and thus A(n,k) < prime(k)^n.

Examples

			A(4,1) = 5: The degree-4 irreducible polynomials p over GF(prime(1)) = GF(2) are 1+x+x^2+x^3+x^4, 1+x+x^4, 1+x^3+x^4. Their orders (i.e., the smallest integer e for which p divides x^e+1) are 5, 15, 15, and the minimal order is 5. (1+x+x^2+x^3+x^4) * (1+x) == x^5+1 (mod 2).
Square array A(n,k) begins:
    1,    1,     1,    1,   1,       1,        1,   1, ...
    3,    4,     3,    4,   3,       7,        3,   4, ...
    7,   13,    31,    9,   7,       9,      307,  27, ...
    5,    5,    13,    5,  16,       5,        5,  16, ...
   31,   11,    11, 2801,  25,   30941,    88741, 151, ...
    9,    7,     7,   36,   9,      63,        7,   7, ...
  127, 1093, 19531,   29,  43, 5229043, 25646167, 701, ...
   17,   32,    32,   64,  32,      32,      128,  17, ...
		

Crossrefs

Columns k=1-10 are first columns of: A059912, A212906, A212485, A212486, A218336, A218337, A218338, A218339, A218340, A218341.
Cf. A212737 (all orders).

Programs

  • Maple
    with(numtheory):
    M:= proc(n, i) option remember;
          divisors(ithprime(i)^n-1) minus U(n-1, i)
        end:
    U:= proc(n, i) option remember;
          `if`(n=0, {}, M(n, i) union U(n-1, i))
        end:
    A:= (n, k)-> min(M(n, k)[]):
    seq(seq(A(n, d+1-n), n=1..d), d=1..14);
  • Mathematica
    M[n_, i_] := M[n, i] = Divisors[Prime[i]^n - 1] ~Complement~ U[n-1, i]; U[n_, i_] := U[n, i] = If[n == 0, {}, M[n, i] ~Union~ U[n-1, i]]; A[n_, k_] := Min[M[n, k]]; Table[Table[A[n, d+1-n], {n, 1, d}], {d, 1, 14}] // Flatten (* Jean-François Alcover, Dec 13 2013, translated from Maple *)

Formula

A(n,k) = min(M(n,k)) with M(n,k) = {d : d|(prime(k)^n-1)} \ U(n-1,k) and U(n,k) = M(n,k) union U(n-1,k) for n>0, U(0,k) = {}.

A212906 Triangle T(n,k) of orders of degree-n irreducible polynomials over GF(3) listed in ascending order.

Original entry on oeis.org

1, 2, 4, 8, 13, 26, 5, 10, 16, 20, 40, 80, 11, 22, 121, 242, 7, 14, 28, 52, 56, 91, 104, 182, 364, 728, 1093, 2186, 32, 41, 82, 160, 164, 205, 328, 410, 656, 820, 1312, 1640, 3280, 6560, 757, 1514, 9841, 19682, 44, 61, 88, 122, 244, 484, 488, 671, 968, 1342
Offset: 1

Views

Author

Boris Putievskiy, May 29 2012

Keywords

Comments

The elements m of row n, are also solutions to the equation: multiplicative order of 3 mod m = n, with gcd(m,3) = 1, cf. A053446.

Examples

			Triangle T(n,k) begins:
1,   2;
4,   8;
13, 26;
5,  10,  16,  20, 40, 80;
11, 22, 121, 242;
7,  14,  28,  52, 56, 91, 104, 182, 364, 728;
		

References

  • R. Lidl and H. Niederreiter, Finite Fields, 2nd ed., Cambridge Univ. Press, 1997, Table C, pp. 555-557.
  • V. I. Arnol'd, Topology and statistics of formulas of arithmetics, Uspekhi Mat. Nauk, 58:4(352) (2003), 3-28

Crossrefs

Column k=2 of A212737.
Column k=1 gives: A218356.

Programs

  • Maple
    with(numtheory):
    M:= proc(n) option remember;
          divisors(3^n-1) minus U(n-1)
        end:
    U:= proc(n) option remember;
          `if`(n=0, {}, M(n) union U(n-1))
        end:
    T:= n-> sort([M(n)[]])[]:
    seq(T(n), n=1..15);  # Alois P. Heinz, Jun 02 2012
  • Mathematica
    M[n_] := M[n] = Divisors[3^n - 1] ~Complement~ U[n - 1];
    U[n_] := U[n] = If[n == 0, {}, M[n] ~Union~ U[n - 1]];
    T[n_] := Sort[M[n]]; Array[T, 15] // Flatten (* Jean-François Alcover, Jun 10 2018, after Alois P. Heinz *)

Formula

T(n,k) = k-th smallest element of M(n) with M(n) = {d : d | (3^n-1)} \ (M(1) U M(2) U ... U M(i-1)) for n>1, M(1) = {1,2}.
|M(n)| = Sum_{d|n} mu(n/d)*tau(3^d-1) = A059885(n).

A108974 Sort the primes (except 2) according to the multiplicative order of 2 modulo that prime. If two primes have the same order of 2, they are arranged numerically.

Original entry on oeis.org

3, 7, 5, 31, 127, 17, 73, 11, 23, 89, 13, 8191, 43, 151, 257, 131071, 19, 524287, 41, 337, 683, 47, 178481, 241, 601, 1801, 2731, 262657, 29, 113, 233, 1103, 2089, 331, 2147483647, 65537, 599479, 43691, 71, 122921, 37, 109, 223, 616318177, 174763, 79
Offset: 1

Views

Author

Douglas Stones (dssto1(AT)student.monash.edu.au), Jul 27 2005

Keywords

Comments

Or, primitive prime divisors of the Mersenne numbers 2^n-1 (see A000225) in their order of occurrence.
Of course the Mersenne primes 2^p-1 (cf. A000043) appear in this sequence.
If all odd positive numbers, not just the odd primes, are sorted in this way, the result is A059912. - Jeppe Stig Nielsen, Feb 13 2020

Examples

			The order of 2 modulo 3 is 2 and the order of 2 modulo 7 is 3. So 3 comes before 7.
		

Crossrefs

Programs

  • Mathematica
    a = 1; DeleteDuplicates[Flatten[#[[All, 1]] & /@ FactorInteger[Table[a = 2 a + 1, {i, 1, 30}]]]] (* Horst H. Manninger, Mar 20 2021 *)
  • PARI
    do(n)=my(v=List(),P=1,g,t,f); for(k=2,n, t=2^k-1; g=P; while((g=gcd(g,t))>1, t/=g); f=factor(t)[,1]; for(i=1,#f, listput(v,f[i])); P*=t); Vec(v) \\ Charles R Greathouse IV, Sep 23 2016

Extensions

More terms from Martin Fuller, Sep 25 2006

A212485 Triangle T(n,k) of orders of degree-n irreducible polynomials over GF(5) listed in ascending order.

Original entry on oeis.org

1, 2, 4, 3, 6, 8, 12, 24, 31, 62, 124, 13, 16, 26, 39, 48, 52, 78, 104, 156, 208, 312, 624, 11, 22, 44, 71, 142, 284, 781, 1562, 3124, 7, 9, 14, 18, 21, 28, 36, 42, 56, 63, 72, 84, 93, 126, 168, 186, 217, 248, 252, 279, 372, 434, 504, 558, 651, 744, 868, 1116
Offset: 1

Views

Author

Boris Putievskiy, Jun 02 2012

Keywords

Comments

The elements m of row n, are also solutions to the equation: multiplicative order of 5 mod m = n, with gcd(m,5) = 1, cf. A050977.

Examples

			Triangle T(n,k) begins:
   1,  2,   4;
   3,  6,   8, 12,  24;
  31, 62, 124;
  13, 16,  26, 39,  48,  52,  78,  104,  156, 208, 312, 624;
  11, 22,  44, 71, 142, 284, 781, 1562, 3124;
  ...
		

References

  • R. Lidl and H. Niederreiter, Finite Fields, 2nd ed., Cambridge Univ. Press, 1997, Table C, pp. 557-560.

Crossrefs

Column k=3 of A212737.
Column k=1 gives: A218357.

Programs

  • Maple
    with(numtheory):
    M:= proc(n) option remember;
          `if`(n=1, {1, 2, 4}, divisors(5^n-1) minus U(n-1))
        end:
    U:= proc(n) option remember;
          `if`(n=0, {}, M(n) union U(n-1))
        end:
    T:= n-> sort([M(n)[]])[]:
    seq(T(n), n=1..8);
  • Mathematica
    M[n_] := M[n] = If[n == 1, {1, 2, 4}, Divisors[5^n-1] ~Complement~ U[n-1]];
    U[n_] := U[n] = If[n == 0, {}, M[n] ~Union~ U[n - 1]];
    T[n_] := Sort[M[n]]; Array[T, 8] // Flatten (* Jean-François Alcover, Jun 10 2018, from Maple *)

Formula

T(n,k) = k-th smallest element of M(n) with M(n) = {d : d | (5^n-1)} \ (M(1) U M(2) U ... U M(i-1)) for n>1, M(1) = {1,2,4}.
|M(n)| = Sum_{d|n} mu(n/d)*tau(5^d-1) = A059887.

A212486 Triangle T(n,k) of orders of degree-n irreducible polynomials over GF(7) listed in ascending order.

Original entry on oeis.org

1, 2, 3, 6, 4, 8, 12, 16, 24, 48, 9, 18, 19, 38, 57, 114, 171, 342, 5, 10, 15, 20, 25, 30, 32, 40, 50, 60, 75, 80, 96, 100, 120, 150, 160, 200, 240, 300, 400, 480, 600, 800, 1200, 2400, 2801, 5602, 8403, 16806, 36, 43, 72, 76, 86, 129, 144, 152, 172, 228, 258
Offset: 1

Views

Author

Boris Putievskiy, Jun 02 2012

Keywords

Comments

The elements m of row n, are also solutions to the equation: multiplicative order of 7 mod m = n, with gcd(m,7) = 1, cf. A053450.

Examples

			Triangle T(n,k) begins:
  1,  2,  3,  6;
  4,  8, 12, 16, 24,  48;
  9, 18, 19, 38, 57, 114, 171, 342;
  5, 10, 15, 20, 25,  30,  32,  40, 50, 60, 75, 80, 96, 100, 120, 150, 160, 200, 240, 300, 400, 480, 600, 800, 1200, 2400;
  ...
		

References

  • R. Lidl and H. Niederreiter, Finite Fields, 2nd ed., Cambridge Univ. Press, 1997, Table C, pp. 560-562.
  • V. I. Arnol'd, Topology and statistics of formulas of arithmetics, Uspekhi Mat. Nauk, 58:4(352) (2003), 3-28

Crossrefs

Column k=4 of A212737.
Column k=1 gives: A218358.

Programs

  • Maple
    with(numtheory):
    M:= proc(n) option remember;
          `if`(n=1, {1, 2, 3, 6}, divisors(7^n-1) minus U(n-1))
        end:
    U:= proc(n) option remember;
          `if`(n=0, {}, M(n) union U(n-1))
        end:
    T:= n-> sort([M(n)[]])[]:
    seq(T(n), n=1..7);
  • Mathematica
    M[n_] := M[n] = If[n == 1, {1, 2, 3, 6}, Divisors[7^n - 1] ~Complement~ U[n - 1]];
    U[n_] := U[n] = If[n == 0, {}, M[n] ~Union~ U[n - 1]];
    T[n_] := Sort[M[n]];
    Table[T[n], {n, 1, 7}] // Flatten (* Jean-François Alcover, Sep 24 2022, from Maple code *)

Formula

T(n,k) = k-th smallest element of M(n) with M(n) = {d : d | (7^n-1)} \ (M(1) U M(2) U ... U M(i-1)) for n>1, M(1) = {1,2,3,6}.
|M(n)| = Sum_{d|n} mu(n/d)*tau(7^d-1) = A059889(n).

A212953 Minimal order of degree-n irreducible polynomials over GF(2).

Original entry on oeis.org

1, 3, 7, 5, 31, 9, 127, 17, 73, 11, 23, 13, 8191, 43, 151, 257, 131071, 19, 524287, 25, 49, 69, 47, 119, 601, 2731, 262657, 29, 233, 77, 2147483647, 65537, 161, 43691, 71, 37, 223, 174763, 79, 187, 13367, 147, 431, 115, 631, 141, 2351, 97, 4432676798593, 251
Offset: 1

Views

Author

Alois P. Heinz, Jun 01 2012

Keywords

Comments

a(n) = smallest odd m such that A002326((m-1)/2) = n. - Thomas Ordowski, Feb 04 2014
For n > 1; n < a(n) < 2^n, wherein a(n) = n+1 iff n+1 is A001122 a prime with primitive root 2, or a(n) = 2^n-1 iff n is a Mersenne exponent A000043. - Thomas Ordowski, Feb 08 2014

Examples

			For n=4 the degree-4 irreducible polynomials p over GF(2) are 1+x+x^2+x^3+x^4, 1+x+x^4, 1+x^3+x^4. Their orders (i.e., the smallest integer e for which p divides x^e+1) are 5, 15, 15. (Example: (1+x+x^2+x^3+x^4) * (1+x) == x^5+1 (mod 2)). Thus the minimal order is 5 and a(4) = 5.
		

References

  • W. Narkiewicz, Elementary and Analytic Theory of Algebraic Numbers, Springer 2004, Third Edition, 4.3 Factorization of Prime Ideals in Extensions. More About the Class Group (Theorem 4.33), 4.4 Notes to Chapter 4 (Theorem 4.40). - Regarding the first comment.

Crossrefs

Programs

  • Maple
    with(numtheory):
    M:= proc(n) option remember;
          divisors(2^n-1) minus U(n-1)
        end:
    U:= proc(n) option remember;
          `if`(n=0, {}, M(n) union U(n-1))
        end:
    a:= n-> min(M(n)[]):
    seq(a(n), n=1..50);
  • Mathematica
    M[n_] := M[n] = Divisors[2^n-1] ~Complement~ U[n-1];
    U[n_] := U[n] = If[n == 0, {}, M[n] ~Union~ U[n-1]];
    a[n_] := Min[M[n]];
    Array[a, 50] (* Jean-François Alcover, Mar 22 2017, translated from Maple *)

Formula

a(n) = min(M(n)) with M(n) = {d : d|(2^n-1)} \ U(n-1) and U(n) = M(n) union U(n-1) for n>0, U(0) = {}.
a(n) = A059912(n,1) = A213224(n,1).
Showing 1-9 of 9 results.