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 1-3 of 3 results.

A293951 Number of linear extensions of a poset whose Hasse diagram consists of n binary shrubs with type B_n joins.

Original entry on oeis.org

1, 9, 477, 74601, 25740261, 16591655817, 17929265150637, 30098784753112329, 74180579084559895221, 256937013876000351610089, 1208025937371403268201735037, 7494692521096248546330688437801, 59931935202159196095445595508666501
Offset: 0

Views

Author

N. J. A. Sloane, Oct 29 2017

Keywords

Crossrefs

Cf. A000182 (m=2), this seq (m=3), A273352 (m=4), A318258 (m=5).

Programs

  • Mathematica
    LMLlist[m_, len_] := Table[(-1)^(n + 1) (m n)!, {n, 1, len}]*
    Delete [CoefficientList[Series[Log[MittagLefflerE[m, z]], {z, 0, len}], z], 1];
    LMLlist[3, 13] (* Peter Luschny, Aug 26 2018 *)

Extensions

Terms a(11) and beyond from Lars Blomberg, Oct 31 2017

A273352 a(n) = 2^(2n+2) F(n) where F(n) is Ramanujan's F(n) = Sum_{k>=1} k^(4n-1)/(e^(Pi*k)-1) - 16^n* Sum_{k>=1} k^(4n-1)/(e^(4*Pi*k)-1).

Original entry on oeis.org

1, 34, 11056, 14873104, 56814228736, 495812444583424, 8575634961418940416, 265929039218907754399744, 13722623393637762299131396096, 1112372064432735526930220874072064, 135292015985218004848567636630910795776, 23782283324940089109797537284278352042000384
Offset: 1

Views

Author

Marko Riedel, May 20 2016

Keywords

Comments

Bisection of the reduced tangent numbers, A002105. This follows from the formulas. - Franklin T. Adams-Watters, May 22 2016

Crossrefs

Cf. A002105.
Cf. A000182 (m=2), A293951 (m=3), this seq (m=4), A318258 (m=5).

Programs

  • Maple
    S := proc(n, k) option remember;
    if k=0 then `if`(n=0, 1, 0) else S(n, k-1) + S(n-1, n-k) fi end:
    A273352 := n -> S(4*n-1, 4*n-1)/2^(2*n-1):
    seq(A273352(n), n=1..12); # Peter Luschny, Jan 18 2017
  • Mathematica
    Table[2^(2*n + 2)*BernoulliB[4*n]*(1 - 2^(4*n))/(8*n), {n, 1, 10}] (* G. C. Greubel, May 21 2016 *)
    (* Function LMLlist defined in A293951 *)
    LMLlist[4, 13] (* Peter Luschny, Aug 26 2018 *)

Formula

a(n) = 2^{2*n+2} * Bernoulli(4*n) * (1-2^(4*n))/(8*n).

A318253 Coefficient of x of the OmegaPolynomials (A318146), T(n, k) = [x] P(n, k) with n>=1 and k>=0, square array read by ascending antidiagonals.

Original entry on oeis.org

0, 0, 1, 0, 1, 0, 0, 1, -2, 0, 0, 1, -9, 16, 0, 0, 1, -34, 477, -272, 0, 0, 1, -125, 11056, -74601, 7936, 0, 0, 1, -461, 249250, -14873104, 25740261, -353792, 0, 0, 1, -1715, 5699149, -2886735625, 56814228736, -16591655817, 22368256, 0, 0, 1, -6434, 132908041, -574688719793, 122209131374375, -495812444583424, 17929265150637, -1903757312, 0
Offset: 1

Views

Author

Peter Luschny, Aug 22 2018

Keywords

Comments

Because in the case n=2 these numbers are the classical signed tangent numbers (A000182) we call T(n, k) also 'generalized tangent numbers' when studied in connection with generalized Bernoulli numbers.

Examples

			[n\k][0  1     2        3              4                   5  ...]
------------------------------------------------------------------
[1]   0, 1,    0,       0,             0,                  0, ...  [A063524]
[2]   0, 1,   -2,      16,          -272,               7936, ...  [A000182]
[3]   0, 1,   -9,     477,        -74601,           25740261, ...  [A293951]
[4]   0, 1,  -34,   11056,     -14873104,        56814228736, ...  [A273352]
[5]   0, 1, -125,  249250,   -2886735625,    122209131374375, ...  [A318258]
[6]   0, 1, -461, 5699149, -574688719793, 272692888959243481, ...
        [A010763]
		

Crossrefs

Programs

  • Maple
    # Prints square array row-wise. The function OmegaPolynomial is defined in A318146.
    for n from 1 to 6 do seq(coeff(OmegaPolynomial(n, k), x, 1), k=0..6) od;
    # In the sequence format:
    0, seq(seq(coeff(OmegaPolynomial(n-k+1, k), x, 1), k=0..n), n=1..9);
    # Alternatively, based on the recurrence of the André numbers:
    ANum := proc(m, n) option remember; if n = 0 then return 1 fi;
    `if`(modp(n, m) = 0, -1, 1);  [seq(m*k, k=0..(n-1)/m)];
    %%*add(binomial(n, k)*ANum(m, k), k in %) end:
    TNum := proc(n,k) if k=1 then 1 elif k=0 or n=1 then 0 else ANum(n, n*k-1) fi end:
    for n from 1 to 6 do seq(TNum(n, k), k = 0..6) od;
  • Mathematica
    OmegaPolynomial[m_, n_] := Module[{S}, S = Series[MittagLefflerE[m, z]^x, {z, 0, 10}]; Expand[(m*n)! Coefficient[S, z, n]]];
    T[n_, k_] := D[OmegaPolynomial[n, k], x] /. x -> 0;
    Table[T[n - k, k], {n, 1, 10}, {k, 0, n - 1}] // Flatten (* Jean-François Alcover, Nov 27 2023 *)
  • Sage
    # Prints the array row-wise. The function OmegaPolynomial is in A318146.
    for m in (1..6):
        print([0] + [list(OmegaPolynomial(m, n))[1] for n in (1..6)])
    # Alternatively, based on the recurrence of the André numbers:
    @cached_function
    def ANum(m, n):
        if n == 0: return 1
        t = [m*k for k in (0..(n-1)//m)]
        s = sum(binomial(n, k)*ANum(m, k) for k in t)
        return -s if m.divides(n) else s
    def TNum(m, n):
        if n == 1: return 1
        if n == 0 or m == 1: return 0
        return ANum(m, m*n-1)
    for m in (1..6): print([TNum(m, n) for n in (0..6)])

Formula

T(n, k) is the derivative of OmegaPolynomial(n, k) evaluated at x = 0.
Apart from the border cases n=1 and k=0 the generalized tangent numbers are a subset of the André numbers A181937; more precisely: T(n, k) is 1 if k = 1 else if k = 0 or n = 1 then T(n, k) = 0 else T(n,k) = (-1)^(n+1)*A181937(n, n*k-1).
Showing 1-3 of 3 results.