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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A362585 Triangle read by rows, T(n, k) = A000670(n) * binomial(n, k).

Original entry on oeis.org

1, 1, 1, 3, 6, 3, 13, 39, 39, 13, 75, 300, 450, 300, 75, 541, 2705, 5410, 5410, 2705, 541, 4683, 28098, 70245, 93660, 70245, 28098, 4683, 47293, 331051, 993153, 1655255, 1655255, 993153, 331051, 47293, 545835, 4366680, 15283380, 30566760, 38208450, 30566760, 15283380, 4366680, 545835
Offset: 0

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Author

Peter Luschny, Apr 26 2023

Keywords

Examples

			[0]    1;
[1]    1,     1;
[2]    3,     6,     3;
[3]   13,    39,    39,    13;
[4]   75,   300,   450,   300,    75;
[5]  541,  2705,  5410,  5410,  2705,   541;
[6] 4683, 28098, 70245, 93660, 70245, 28098, 4683;
		

Crossrefs

Family of triangles: A055372 (m=0, Pascal), this sequence (m=1, Fubini), A362586 (m=2, Joffe), A362849 (m=3, A278073).
Cf. A000670 (column 0 and main diagonal), A216794 (row sums).

Programs

  • SageMath
    def TransOrdPart(m, n) -> list[int]:
        @cached_function
        def P(m: int, n: int):
            R = PolynomialRing(ZZ, "x")
            if n == 0: return R(1)
            return R(sum(binomial(m * n, m * k) * P(m, n - k) * x
                     for k in range(1, n + 1)))
        T = P(m, n)
        def C(k) -> int:
            return sum(T[j] * binomial(n, k) for j in range(n + 1))
        return [C(k) for k in range(n+1)]
    def A362585(n) -> list[int]: return TransOrdPart(1, n)
    for n in range(6): print(A362585(n))

A346432 a(0) = 1; a(n) = n! * Sum_{k=0..n-1} (n-k+1) * a(k) / k!.

Original entry on oeis.org

1, 2, 14, 144, 1968, 33600, 688320, 16450560, 449326080, 13806858240, 471395635200, 17703899136000, 725338710835200, 32193996432998400, 1538840509503897600, 78808952068374528000, 4305129487814098944000, 249876735246162984960000, 15356385691181506363392000
Offset: 0

Views

Author

Ilya Gutkovskiy, Jul 17 2021

Keywords

Crossrefs

Programs

  • Mathematica
    a[0] = 1; a[n_] := a[n] = n! Sum[(n - k + 1) a[k]/k!, {k, 0, n - 1}]; Table[a[n], {n, 0, 18}]
    nmax = 18; CoefficientList[Series[1/(2 - 1/(1 - x)^2), {x, 0, nmax}], x] Range[0, nmax]!
    Table[Sum[(-1)^(n - k) StirlingS1[n, k] 2^k HurwitzLerchPhi[1/2, -k, 0]/2, {k, 0, n}], {n, 0, 18}]
  • PARI
    my(x='x+O('x^25)); Vec(serlaplace(1 / (2 - 1 / (1 - x)^2))) \\ Michel Marcus, Jul 18 2021

Formula

E.g.f.: 1 / (2 - 1 / (1 - x)^2).
E.g.f.: 1 / (1 - Sum_{k>=1} (k+1) * x^k).
a(0) = 1, a(1) = 2, a(2) = 14; a(n) = 4 * n * a(n-1) - 2 * n * (n-1) * a(n-2).
a(n) = Sum_{k=0..n} (-1)^(n-k) * Stirling1(n,k) * 2^k * A000670(k).
a(n) = n! * A003480(n).

A346433 E.g.f.: 1 / (2 - exp(2*(exp(x) - 1))).

Original entry on oeis.org

1, 2, 14, 142, 1910, 32094, 647126, 15223198, 409276054, 12378827166, 416006542550, 15378483225758, 620176642174742, 27094392220198814, 1274759052849262422, 64259896197635471006, 3455259407744574799254, 197401403111903906001310, 11941074177046918285056470
Offset: 0

Views

Author

Ilya Gutkovskiy, Jul 17 2021

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 18; CoefficientList[Series[1/(2 - Exp[2 (Exp[x]- 1)]), {x, 0, nmax}], x] Range[0, nmax]!
    a[0] = 1; a[n_] := a[n] = Sum[Binomial[n, k] BellB[k, 2] a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 18}]
    Table[Sum[StirlingS2[n, k] 2^k HurwitzLerchPhi[1/2, -k, 0]/2, {k, 0, n}], {n, 0, 18}]
  • PARI
    my(x='x+O('x^25)); Vec(serlaplace(1 / (2 - exp(2*(exp(x) - 1))))) \\ Michel Marcus, Jul 18 2021

Formula

a(0) = 1; a(n) = Sum_{k=1..n} binomial(n,k) * A001861(k) * a(n-k).
a(n) = Sum_{k=0..n} Stirling2(n,k) * 2^k * A000670(k).
a(n) ~ n! / (2*(2+log(2)) * (log(1+log(2)/2))^(n+1)). - Vaclav Kotesovec, Jul 27 2021

A382753 Expansion of e.g.f. 3/(5 - 2*exp(3*x)).

Original entry on oeis.org

1, 2, 14, 138, 1806, 29562, 580734, 13309578, 348611886, 10272416922, 336326121054, 12112707922218, 475894244100366, 20255443904321082, 928448378212678974, 45597074777924954058, 2388608236671667179246, 132947999835258872046042, 7835059049893316949502494
Offset: 0

Views

Author

Seiichi Manyama, Jun 03 2025

Keywords

Crossrefs

Programs

  • PARI
    a(n) = (-3)^(n+1)*polylog(-n, 5/2)/5;

Formula

a(n) = (-3)^(n+1)/5 * Li_{-n}(5/2), where Li_{n}(x) is the polylogarithm function.
a(n) = 3^(n+1)/5 * Sum_{k>=0} k^n * (2/5)^k.
a(n) = Sum_{k=0..n} 2^k * 3^(n-k) * k! * Stirling2(n,k).
a(n) = (2/5) * A201367(n) = (2/5) * Sum_{k=0..n} 5^k * (-3)^(n-k) * k! * Stirling2(n,k) for n > 0.
a(0) = 1; a(n) = 2 * Sum_{k=1..n} 3^(k-1) * binomial(n,k) * a(n-k).
a(0) = 1; a(n) = 2 * a(n-1) + 5 * Sum_{k=1..n-1} (-3)^(k-1) * binomial(n-1,k) * a(n-k).

A337027 a(n) = (1/2) * Sum_{k>=0} (2*k + n)^n / 2^k.

Original entry on oeis.org

1, 3, 24, 293, 4784, 97687, 2393472, 68405073, 2233928448, 82063263371, 3349249267712, 150353137462717, 7362889615257600, 390601858379350815, 22315011551291080704, 1365896953310909493929, 89179296762081886011392, 6186383336743041502051219
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 11 2020

Keywords

Crossrefs

Programs

  • Mathematica
    Table[2^(n - 1) HurwitzLerchPhi[1/2, -n, n/2], {n, 0, 17}]
    Table[n! SeriesCoefficient[Exp[n x]/(2 - Exp[2 x]), {x, 0, n}], {n, 0, 17}]

Formula

a(n) = n! * [x^n] exp(n*x) / (2 - exp(2*x)).
a(n) = Sum_{k=0..n} binomial(n,k) * n^k * A216794(n-k).
Previous Showing 11-15 of 15 results.