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.

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A356490 a(n) is the determinant of a symmetric Toeplitz matrix M(n) whose first row consists of prime(1), prime(2), ..., prime(n).

Original entry on oeis.org

1, 2, -5, 12, -19, -22, 1143, -4284, 14265, -46726, -84405, 1306096, 32312445, 522174906, 4105967871, 5135940112, -642055973735, -2832632334858, 14310549077571, 380891148658140, 4888186898996125, -49513565563840210, 383405170118692791, -2517836083641473036, -3043377347606882055
Offset: 0

Views

Author

Stefano Spezia, Aug 09 2022

Keywords

Comments

Conjecture: abs(a(n)) is prime only for n = 1, 2, and 4.

Examples

			For n = 1 the matrix M(1) is
    2
with determinant a(1) = 2.
For n = 2 the matrix M(2) is
    2, 3
    3, 2
with determinant a(2) = -5.
For n = 3 the matrix M(3) is
    2, 3, 5
    3, 2, 3
    5, 3, 2
with determinant a(3) = 12.
		

Crossrefs

Cf. A005843 (trace of M(n)), A309131 (k-superdiagonal sum of M(n)), A356483 (hafnian of M(2*n)), A356491 (permanent of M(n)).

Programs

  • Maple
    A356490 := proc(n)
        local T,c ;
        if n =0 then
            return 1 ;
        end if;
        T := LinearAlgebra[ToeplitzMatrix]([seq(ithprime(c),c=1..n)],n,symmetric) ;
        LinearAlgebra[Determinant](T) ;
    end proc:
    seq(A356490(n),n=0..15) ; # R. J. Mathar, Jan 31 2023
  • Mathematica
    k[i_]:=Prime[i]; M[ n_]:=ToeplitzMatrix[Array[k, n]]; a[n_]:=Det[M[n]]; Join[{1},Table[a[n],{n,24}]]
  • PARI
    a(n) = matdet(apply(prime, matrix(n,n,i,j,abs(i-j)+1))); \\ Michel Marcus, Aug 12 2022
    
  • Python
    from sympy import Matrix, prime
    def A356490(n): return Matrix(n,n,[prime(abs(i-j)+1) for i in range(n) for j in range(n)]).det() # Chai Wah Wu, Aug 12 2022

Formula

A350955(n) <= a(n) <= A350956(n).

A356491 a(n) is the permanent of a symmetric Toeplitz matrix M(n) whose first row consists of prime(1), prime(2), ..., prime(n).

Original entry on oeis.org

1, 2, 13, 184, 4745, 215442, 14998965, 1522204560, 208682406913, 37467772675962, 8809394996942597, 2597094620811897948, 954601857873086235553, 428809643170145564168434, 229499307540038336275308821, 144367721963876506217872778284, 106064861375232790889279725340713
Offset: 0

Views

Author

Stefano Spezia, Aug 09 2022

Keywords

Comments

Conjecture: a(n) is prime only for n = 1 and 2.

Examples

			For n = 1 the matrix M(1) is
    2
with permanent a(1) = 2.
For n = 2 the matrix M(2) is
    2, 3
    3, 2
with permanent a(2) = 13.
For n = 3 the matrix M(3) is
    2, 3, 5
    3, 2, 3
    5, 3, 2
with permanent a(3) = 184.
		

Crossrefs

Cf. A005843 (trace of the matrix M(n)), A309131 (k-superdiagonal sum of the matrix M(n)), A356483 (hafnian of the matrix M(2*n)), A356490 (determinant of the matrix M(n)).

Programs

  • Maple
    A356491 := proc(n)
        local c ;
        if n =0 then
            return 1 ;
        end if;
        LinearAlgebra[ToeplitzMatrix]([seq(ithprime(c),c=1..n)],n,symmetric) ;
        LinearAlgebra[Permanent](%) ;
    end proc:
    seq(A356491(n),n=0..15) ; # R. J. Mathar, Jan 31 2023
  • Mathematica
    k[i_]:=Prime[i]; M[ n_]:=ToeplitzMatrix[Array[k, n]]; a[n_]:=Permanent[M[n]]; Join[{1},Table[a[n],{n,16}]]
  • PARI
    a(n) = matpermanent(apply(prime, matrix(n,n,i,j,abs(i-j)+1))); \\ Michel Marcus, Aug 12 2022
    
  • Python
    from sympy import Matrix, prime
    def A356491(n): return Matrix(n,n,[prime(abs(i-j)+1) for i in range(n) for j in range(n)]).per() if n else 1 # Chai Wah Wu, Aug 12 2022

Formula

A351021(n) <= a(n) <= A351022(n).

A330087 Permanent of a square matrix M(n) whose general element M_{i,j} is defined by i*prime(j).

Original entry on oeis.org

1, 2, 24, 1080, 120960, 33264000, 15567552000, 12967770816000, 15768809312256000, 29377291748732928000, 85194146071325491200000, 319563241913541917491200000, 1702632952915351336393113600000, 11797543730750469409867884134400000, 99429698562764956186366527484723200000
Offset: 0

Views

Author

Stefano Spezia, Dec 01 2019

Keywords

Comments

det(M(0)) = 1, det(M(1)) = 2 and det(M(n)) = 0 for n > 1.
The trace of the matrix M(n) is A014285(n).
The antitrace of the matrix M(n) is A014148(n).
The antidiagonal of the matrix M(n) is the n-th row of the triangle A309131.

Examples

			For n = 1 the matrix M(1) is
  2
with permanent a(1) = 2.
For n = 2 the matrix M(2) is
  2, 3
  4, 6
with permanent a(2) = 24.
For n = 3 the matrix M(3) is
  2,  3,  5
  4,  6, 10
  6,  9, 15
with permanent a(3) = 1080.
		

Crossrefs

Programs

  • Maple
    with(LinearAlgebra):
    a:= n-> `if`(n=0, 1, Permanent(Matrix(n, (i, j)-> i*ithprime(j)))):
    seq(a(n), n=0..14);  # Alois P. Heinz, Dec 04 2019
  • Mathematica
    M[i_, j_, n_] := i*Prime[j]; a[n_] := If[n==0,1,Permanent[Table[M[i, j, n], {i, n}, {j, n}]]]; Array[a, 14, 0]
  • PARI
    a(n) = matpermanent(matrix(n, n, i, j, i*prime(j))); \\ Michel Marcus, Dec 04 2019

Extensions

a(0) = 1 prepended by Michel Marcus, Dec 04 2019
Showing 1-3 of 3 results.