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.

Previous Showing 31-36 of 36 results.

A370411 Square array T(n, k) = denominator( zeta_r(2*n) * sqrt(A003658(k + 2)) / Pi^(4*n) ), read by antidiagonals, where zeta_r is the Dedekind zeta-function over r and r is the real quadratic field with discriminant A003658(k + 2).

Original entry on oeis.org

1, 75, 1, 16875, 24, 1, 221484375, 34560, 18, 1, 116279296875, 116121600, 58320, 39, 1, 12950606689453125, 780337152000, 440899200, 296595, 51, 1, 4861333986053466796875, 8899589151129600, 6666395904000, 68420017575, 663255, 63, 1, 677114376628875732421875
Offset: 0

Views

Author

Thomas Scheuerle, Feb 22 2024

Keywords

Examples

			The array begins:
           1,            1,             1,              1,                 1
          75,           24,            18,             39,                51
       16875,        34560,         58320,         296595,            663255
   221484375,    116121600,     440899200,    68420017575,       20126472975
116279296875, 780337152000, 6666395904000, 93393323989875, 10382542981248375
		

Crossrefs

Cf. A370412 (numerators).
Cf. A002432 (denominators zeta(2*n)/Pi^(2*n)).
Cf. A046988 (numerators zeta(2*n)/Pi^(2*n)).
Coefficients of Dedekind zeta functions for real quadratic number fields of discriminants 5, 8, 12, 13, 17, 21, 24, 28, 29, 33, 37, 40 are A035187, A035185, A035194, A035195, A035199, A035203, A035188, A035210, A035211, A035215, A035219, A035192, respectively.

Programs

  • PARI
    \p 700
    row(n) = {v=[]; for(k=2, 30, if(isfundamental(k), v=concat(v, denominator(bestappr(sqrt(k)*lfun(x^2-(k%2)*x-floor(k/4), 2*n)/Pi^(4*n)))))); v}
    z(n,d) = if(n == 0, 0,(1/(-2*n))*bernfrac(2*n)*d^(2*n-1)*sum(k=1,d-1, kronecker(d, k)*subst(bernpol(2*n),x,k/d)*(1/(-2*n))))
    row(n) = {v=[]; for(k=2, 100, if(isfundamental(k), v=concat(v, denominator((2^(n*4)*n^2*z(n,k))/((2*n)!^2 * (k^(2*n-1))))))); v} \\ more accuracy here
    
  • Sage
    # Only suitable for small n and k
    def T(n, k):
        discs = [fundamental_discriminant(i) for i in range(1, 4*k+10)]
        D = sorted(list(set(discs)))[k+1]
        zetaK = QuadraticField(D).zeta_function(1000)
        val = (zetaK(2*n)*sqrt(D)/(pi^(4*n))).n(1000).nearby_rational(2^-900)
        return val.denominator() # Robin Visser, Mar 19 2024

Formula

T(n, k) = denominator( 2^(n*4) * n^2 * zeta_r(1 - 2*n) /((2*n)!^2 * A003658(k + 2)^(2*n - 1)) ), where zeta_r is the Dedekind zeta-function over r and r is the real quadratic field with discriminant A003658(k + 2).
T(n, 0) = denominator((5^(-2*n)*(zeta(2*n, 1/5) - zeta(2*n, 2/5) - zeta(2*n, 3/5) + zeta(2*n, 4/5) ))*zeta(2*n)*sqrt(5)*Pi^(-4*n)). A sum of Hurwitz zeta functions with signs according A080891.
T(n, 1) = denominator( 2^(n*4) * n^2 * zeta(1 - 2*n) * (-1)^n * A000464(n+1) /((2*n)!^2 * 8^(2*n - 1)) ).
T(n, 2) = denominator( 2^(n*4) * n^2 * zeta(1 - 2*n) * (-1)^n * A000191(n+1) /((2*n)!^2 * 12^(2*n - 1)) ).
T(n, 3) = denominator((13^(-2*n)*(zeta(2*n, 1/13) - zeta(2*n, 2/13) + zeta(2*n, 3/13) + zeta(2*n, 4/13) - zeta(2*n, 5/13) - zeta(2*n, 6/13) - zeta(2*n, 7/13) - zeta(2*n, 8/13) + zeta(2*n, 9/13) + zeta(2*n, 10/13) - zeta(2*n, 11/13) + zeta(2*n, 12/13) ))*zeta(2*n)*sqrt(13)*Pi^(-4*n)). A sum of Hurwitz zeta functions with signs according the Dirichlet character X13(12,.).
T(n, 6) = denominator( 2^(n*4) * n^2 * zeta(1 - 2*n) * (-1)^n * A000411(n+1) /((2*n)!^2 * 24^(2*n - 1)) ).
T(n, 7) = denominator( 2^(n*4) * n^2 * zeta(1 - 2*n) * (-1)^n * A064072(n+1) /((2*n)!^2 * 28^(2*n - 1)) ).
T(n, 11) = denominator( 2^(n*4) * n^2 * zeta(1 - 2*n) * (-1)^n * A064075(n+1) /((2*n)!^2 * 40^(2*n - 1)) ).
T(n, k) = denominator( 2^(n*4) * n^2 * zeta(1 - 2*n) * (-1)^n * d(A003658(k+2)/4, n+1) /((2*n)!^2 * 40^(2*n - 1)) ), for all k where A003658(k+2) is a multiple of four (The discriminant of the quadratic field is from 4*A230375). d() are the generalized tangent numbers.
T(0, k) = 1, because for a real quadratic number field the discriminant D is positive, hence the Kronecker symbol (D/-1) = 1. This means the associated Dirichlet L-function will be zero at s = 0 inside the expression zeta_r(s) = zeta(s)*L(s, x).

A370412 Square array T(n, k) = numerator( zeta_r(2*n) * sqrt(A003658(k + 2)) / Pi^(4*n) ), read by antidiagonals, where zeta_r is the Dedekind zeta-function over r and r is the real quadratic field with discriminant A003658(k + 2).

Original entry on oeis.org

0, 2, 0, 4, 1, 0, 536, 11, 1, 0, 2888, 361, 23, 2, 0, 3302008, 24611, 1681, 116, 4, 0, 12724582576, 2873041, 257543, 267704, 328, 4, 0, 18194938976, 27233033477, 67637281, 3741352, 92656, 88, 1, 0, 875222833138832, 11779156811, 18752521534133, 1156377368, 479214352, 287536, 29, 2, 0
Offset: 0

Views

Author

Thomas Scheuerle, Feb 22 2024

Keywords

Examples

			The array begins:
          0,           0,              0,               0,                 0
          2,           1,              1,               2,                 4
          4,          11,             23,             116,               328
        536,         361,           1681,          267704,             92656
       2888,       24611,         257543,         3741352,         479214352
    3302008,     2873041,       67637281,      1156377368,       14816172016
12724582576, 27233033477, 18752521534133, 753075777246704, 16476431095568992
		

Crossrefs

Cf. A370411 (denominators).
Cf. A002432 (denominators zeta(2*n)/Pi^(2*n)).
Cf. A046988 (numerators zeta(2*n)/Pi^(2*n)).
Coefficients of Dedekind zeta functions for real quadratic number fields of discriminants 5, 8, 12, 13, 17, 21, 24, 28, 29, 33, 37, 40 are A035187, A035185, A035194, A035195, A035199, A035203, A035188, A035210, A035211, A035215, A035219, A035192, respectively.

Programs

  • PARI
    \p 700
    row(n) = {v=[]; for(k=2, 50, if(isfundamental(k), v=concat(v, numerator(bestappr(sqrt(k)*lfun(x^2-(k%2)*x-floor(k/4), 2*n)/Pi^(4*n)))))); v}
    z(n,d) = if(n == 0, 0,(1/(-2*n))*bernfrac(2*n)*d^(2*n-1)*sum(k=1,d-1, kronecker(d, k)*subst(bernpol(2*n),x,k/d)*(1/(-2*n))))
    row(n) = {v=[]; for(k=2, 100, if(isfundamental(k), v=concat(v, numerator((2^(n*4)*n^2*z(n,k))/((2*n)!^2 * (k^(2*n-1))))))); v} \\ more accuracy here
    
  • Sage
    # Only suitable for small n and k
    def T(n, k):
        discs = [fundamental_discriminant(i) for i in range(1, 4*k+10)]
        D = sorted(list(set(discs)))[k+1]
        zetaK = QuadraticField(D).zeta_function(1000)
        val = (zetaK(2*n)*sqrt(D)/(pi^(4*n))).n(1000).nearby_rational(2^-900)
        return val.numerator() # Robin Visser, Mar 19 2024

Formula

T(n, k) = numerator( 2^(n*4) * n^2 * zeta_r(1 - 2*n) /((2*n)!^2 * A003658(k + 2)^(2*n - 1)) ), where zeta_r is the Dedekind zeta-function over r and r is the real quadratic field with discriminant A003658(k + 2).
T(n, 0) = numerator((5^(-2*n)*(zeta(2*n, 1/5) - zeta(2*n, 2/5) - zeta(2*n, 3/5) + zeta(2*n, 4/5) ))*zeta(2*n)*sqrt(5)*Pi^(-4*n)). A sum of Hurwitz zeta functions with signs according A080891.
T(n, 1) = numerator( 2^(n*4) * n^2 * zeta(1 - 2*n) * (-1)^n * A000464(n+1) /((2*n)!^2 * 8^(2*n - 1)) ).
T(n, 2) = numerator( 2^(n*4) * n^2 * zeta(1 - 2*n) * (-1)^n * A000191(n+1) /((2*n)!^2 * 12^(2*n - 1)) ).
T(n, 3) = numerator((13^(-2*n)*(zeta(2*n, 1/13) - zeta(2*n, 2/13) + zeta(2*n, 3/13) + zeta(2*n, 4/13) - zeta(2*n, 5/13) - zeta(2*n, 6/13) - zeta(2*n, 7/13) - zeta(2*n, 8/13) + zeta(2*n, 9/13) + zeta(2*n, 10/13) - zeta(2*n, 11/13) + zeta(2*n, 12/13) ))*zeta(2*n)*sqrt(13)*Pi^(-4*n)). A sum of Hurwitz zeta functions with signs according the Dirichlet character X13(12,.).
T(n, 6) = numerator( 2^(n*4) * n^2 * zeta(1 - 2*n) * (-1)^n * A000411(n+1) /((2*n)!^2 * 24^(2*n - 1)) ).
T(n, 7) = numerator( 2^(n*4) * n^2 * zeta(1 - 2*n) * (-1)^n * A064072(n+1) /((2*n)!^2 * 28^(2*n - 1)) ).
T(n, 11) = numerator( 2^(n*4) * n^2 * zeta(1 - 2*n) * (-1)^n * A064075(n+1) /((2*n)!^2 * 40^(2*n - 1)) ).
T(n, k) = numerator( 2^(n*4) * n^2 * zeta(1 - 2*n) * (-1)^n * d(A003658(k+2)/4, n+1) /((2*n)!^2 * 40^(2*n - 1)) ), for all k where A003658(k+2) is a multiple of four (The discriminant of the quadratic field is from 4*A230375). d() are the generalized tangent numbers.
T(0, k) = 0, because for a real quadratic number field the discriminant D is positive, hence the Kronecker symbol (D/-1) = 1. This means the associated Dirichlet L-function will be zero at s = 0 inside the expression zeta_r(s) = zeta(s)*L(s, x).

A031366 Number of symmetrically inequivalent coincidence rotations of icosian ring of index n.

Original entry on oeis.org

1, 0, 0, 25, 36, 0, 0, 0, 100, 0, 288, 0, 0, 0, 0, 440, 0, 0, 800, 900, 0, 0, 0, 0, 960, 0, 0, 0, 1800, 0, 2048, 0, 0, 0, 0, 2500, 0, 0, 0, 0, 3528, 0, 0, 7200, 3600, 0, 0, 0, 2550, 0, 0, 0, 0, 0, 10368, 0, 0, 0, 7200, 0, 7688, 0, 0, 7330, 0, 0, 0, 0, 0, 0, 10368, 0, 0, 0, 0, 20000, 0, 0, 12800, 15840, 8362, 0, 0, 0, 0, 0, 0, 0, 16200, 0, 0, 0, 0, 0, 28800, 0, 0, 0, 28800, 23899
Offset: 1

Views

Author

Keywords

Comments

The overall number of coincidence rotations is 7200 times this value. Some symmetrically distinct rotations generate the same coincidence site modules, hence a(n) >= A331143(n). - Andrey Zabolotskiy, Feb 16 2021

Crossrefs

Cf. A331143.

Programs

  • Maple
    read("transforms") :
    # expansion of 1/(1-5^(-s)) in (5.10)
    L1 := [1,seq(0,i=2..200)] :
    for k from 1 do
        if 5^k <= nops(L1) then
            L1 := subsop(5^k=1,L1) ;
        else
            break ;
        end if;
    end do:
    # multiplication with 1/(1-p^(-2s)) in (5.10)
    for i from 1 do
        p := ithprime(i) ;
        if modp(p,5) = 2 or modp(p,5)=3 then
            Laux := [1,seq(0,i=2..200)] :
            for k from 1 do
                if p^(2*k) <= nops(Laux) then
                    Laux := subsop(p^(2*k)=1,Laux) ;
                else
                    break ;
                end if;
            end do:
            L1 := DIRICHLET(L1,Laux) ;
        end if;
        if p > nops(L1) then
            break;
        end if;
    end do:
    # multiplication with 1/(1-p^(-s))^2 in (5.10)
    for i from 1 do
        p := ithprime(i) ;
        if modp(p,5) = 1 or modp(p,5)=4 then
            Laux := [1,seq(0,i=2..200)] :
            for k from 1 do
                if p^k <= nops(Laux) then
                    Laux := subsop(p^k=k+1,Laux) ;
                else
                    break ;
                end if;
            end do:
            L1 := DIRICHLET(L1,Laux) ;
        end if;
        if p > nops(L1) then
            break;
        end if;
    end do:
    # this is now Zeta_L(s), seems to be A035187
    # print(L1) ;
    # generate Zeta_L(s-1)
    L1shft := [seq(op(i,L1)*i,i=1..nops(L1))] ;
    # generate 1/Zeta_L(s)
    L1x := add(op(i,L1)*x^(i-1),i=1..nops(L1)) :
    taylor(1/L1x,x=0,nops(L1)) :
    L1i := gfun[seriestolist](%) ;
    # generate 1/Zeta_L(2s)
    L1i2 := [1,seq(0,i=2..nops(L1))] ;
    for k from 2 to nops(L1i) do
        if k^2 < nops(L1i2) then
            L1i2 := subsop(k^2=op(k,L1i),L1i2) ;
        else
            break ;
        end if;
    end do:
    # generate Zeta_L(s)*Zeta_L(s-1)
    DIRICHLET(L1,L1shft) ;
    # generate Zeta_L(s)*Zeta_L(s-1)/Zeta_L(2s) = Phi(s)
    Phis := DIRICHLET(%,L1i2) ;
    # generate Phis(s-1)
    Phishif := [seq(op(i,Phis)*i,i=1..nops(Phis))] ;
    DIRICHLET(Phis,Phishif) ;

Formula

See Baake (1997) for the Dirichlet g.f.

Extensions

Terms beyond a(36) from R. J. Mathar, Mar 04 2018
New name from Andrey Zabolotskiy, Feb 16 2021

A300382 Dirichlet series for a cubic module of rank 6.

Original entry on oeis.org

1, 0, 0, 8, 6, 0, 0, 0, 10, 0, 24, 0, 0, 0, 0, 32, 0, 0, 40, 48, 0, 0, 0, 0, 30, 0, 0, 0, 60, 0, 64, 0, 0, 0, 0, 80, 0, 0, 0, 0, 84, 0, 0, 192, 60, 0, 0, 0, 51, 0, 0, 0, 0, 0, 144, 0, 0, 0, 120, 0, 124, 0, 0, 130, 0, 0, 0, 0, 0, 0, 144, 0, 0, 0, 0, 320, 0, 0, 160, 192, 91, 0, 0, 0, 0, 0, 0, 0, 180, 0, 0, 0, 0, 0, 240, 0, 0, 0, 240, 239, 204, 0, 0, 0, 0, 0, 0, 0, 220, 0, 0, 0, 0, 0, 0, 480, 0, 0, 0, 0, 405
Offset: 1

Views

Author

R. J. Mathar, Mar 04 2018

Keywords

Comments

Submitted as a substitute for A031365 which appears to display a faulty A031365(16)=24 in the version published 1997.

Crossrefs

Cf. A031365.

Programs

  • Maple
    read("transforms") :
    # expansion of 1/(1-5^(-s)) in (5.10)
    L1 := [1,seq(0,i=2..200)] :
    for k from 1 do
        if 5^k <= nops(L1) then
            L1 := subsop(5^k=1,L1) ;
        else
            break ;
        end if;
    end do:
    # multiplication with 1/(1-p^(-2s)) in (5.10)
    for i from 1 do
        p := ithprime(i) ;
        if modp(p,5) = 2 or modp(p,5)=3 then
            Laux := [1,seq(0,i=2..200)] :
            for k from 1 do
                if p^(2*k) <= nops(Laux) then
                    Laux := subsop(p^(2*k)=1,Laux) ;
                else
                    break ;
                end if;
            end do:
            L1 := DIRICHLET(L1,Laux) ;
        end if;
        if p > nops(L1) then
            break;
        end if;
    end do:
    # multiplication with 1/(1-p^(-s))^2 in (5.10)
    for i from 1 do
        p := ithprime(i) ;
        if modp(p,5) = 1 or modp(p,5)=4 then
            Laux := [1,seq(0,i=2..200)] :
            for k from 1 do
                if p^k <= nops(Laux) then
                    Laux := subsop(p^k=k+1,Laux) ;
                else
                    break ;
                end if;
            end do:
            L1 := DIRICHLET(L1,Laux) ;
        end if;
        if p > nops(L1) then
            break;
        end if;
    end do:
    # this is now Zeta_L(s), seems to be A035187
    # print(L1) ;
    # generate Zeta_L(s-1)
    L1shft := [seq(op(i,L1)*i,i=1..nops(L1))] ;
    # generate 1/Zeta_L(s)
    L1x := add(op(i,L1)*x^(i-1),i=1..nops(L1)) :
    taylor(1/L1x,x=0,nops(L1)) :
    L1i := gfun[seriestolist](%) ;
    # generate 1/Zeta_L(2s)
    L1i2 := [1,seq(0,i=2..nops(L1))] ;
    for k from 2 to nops(L1i) do
        if k^2 < nops(L1i2) then
            L1i2 := subsop(k^2=op(k,L1i),L1i2) ;
        else
            break ;
        end if;
    end do:
    # generate Zeta_L(s)*Zeta_L(s-1)
    DIRICHLET(L1,L1shft) ;
    # generate Zeta_L(s)*Zeta_L(s-1)/Zeta_L(2s)
    L1 := DIRICHLET(%,L1i2) ;
    # generate 1/(1+4^(-s))
    Laux := [1,seq(0,i=2..nops(L1))] :
    for k from 1 do
        if 4^k <= nops(Laux) then
            Laux := subsop(4^k=(-1)^k,Laux) ;
        else
            break;
        end if ;
    end do:
    # generate Zeta_L(s)*Zeta_L(s-1)/Zeta_L(2s)/(1+4^(-s))
    L1 := DIRICHLET(L1,Laux) ;
    # generate 1+4^(1-s)
    Laux := [1,seq(0,i=2..3),4,seq(0,i=5..nops(L1))] ;
    DIRICHLET(L1,Laux) ; # R. J. Mathar, Mar 04 2018

A327785 Square array read by antidiagonals: A(n,k) = Sum_{d|n} (k/d), (n>=1, k>=0), where (m/n) is the Kronecker symbol.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 0, 0, 3, 1, 1, 1, 1, 1, 2, 1, 1, 0, 2, 1, 0, 4, 1, 1, 1, 0, 1, 0, 0, 2, 1, 1, 2, 1, 1, 2, 0, 2, 4, 1, 1, 1, 2, 1, 1, 2, 0, 1, 3, 1, 1, 2, 0, 3, 2, 0, 2, 0, 1, 4, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 0, 2, 1, 1, 0, 2, 3, 0, 4, 0, 0, 3, 0, 0, 6, 1
Offset: 1

Views

Author

Seiichi Manyama, Sep 25 2019

Keywords

Examples

			Square array begins:
   1, 1, 1, 1, 1, 1, 1, 1, ...
   1, 2, 1, 0, 1, 0, 1, 2, ...
   1, 2, 0, 1, 2, 0, 1, 2, ...
   1, 3, 1, 1, 1, 1, 1, 3, ...
   1, 2, 0, 0, 2, 1, 2, 0, ...
   1, 4, 0, 0, 2, 0, 1, 4, ...
   1, 2, 2, 0, 2, 0, 0, 1, ...
   1, 4, 1, 0, 1, 0, 1, 4, ...
		

Crossrefs

Programs

  • Mathematica
    A[n_, k_] := Sum[KroneckerSymbol[k, d], {d, Divisors[n]}];
    Table[A[n - k, k], {n, 1, 13}, {k, n - 1, 0, -1}] // Flatten (* Jean-François Alcover, Sep 25 2019 *)

A161528 Expansion of the q-series Sum_{n >= 0} (-1)^nq^(n(n+1)/2)(1-q)(1-q^2)...(1-q^n)/((1-q^(n+1))(1-q^(n+2))...(1-q^(2n+1))).

Original entry on oeis.org

1, 0, 2, 1, 0, 0, 2, 1, 2, 0, 0, 0, 2, 0, 2, 2, 1, 0, 0, 0, 2, 0, 0, 2, 3, 0, 2, 0, 0, 0, 2, 0, 0, 0, 2, 2, 2, 0, 2, 1, 0, 0, 2, 0, 0, 0, 0, 2, 2, 0, 2, 1, 2, 0, 2, 0, 2, 0, 0, 0, 0, 0, 2, 2, 0, 0, 2, 0, 4, 0, 0, 2, 3, 0, 0, 0, 0, 0, 0, 2, 2, 0, 0, 0, 2, 0, 2, 2, 1, 0, 4, 0, 2, 0, 0, 0, 0, 0, 2, 2
Offset: 0

Views

Author

Jeremy Lovejoy, Jun 12 2009

Keywords

Crossrefs

Programs

  • Mathematica
    f[p_, e_] := If[MemberQ[{2, 3}, Mod[p, 5]], (1 + (-1)^e)/2, e+1]; f[5, e_] := 1; a[0] = 1; a[n_] := Times @@ f @@@ FactorInteger[5*n+1]; Array[a, 100, 0] (* Amiram Eldar, Jan 11 2025 *)
  • PARI
    a(n) = {my(f = factor(5*n+1)); prod(i = 1, #f~, if(f[i, 1] == 5, 1, if(f[i, 1] % 5 == 2 || f[i, 1] % 5 == 3, (1 + (-1)^f[i, 2])/2, f[i, 2] + 1)));} \\ Amiram Eldar, Jan 11 2025

Formula

a(n) = A035187(5n+1).
Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = 4*log(phi)/sqrt(5) = 0.860817..., where phi is the golden ratio (A001622) . - Amiram Eldar, Jan 11 2025
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