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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A301511 Expansion of e.g.f. exp(Sum_{k>=1} psi(k)*x^k/k!), where psi() is the Dedekind psi function (A001615).

Original entry on oeis.org

1, 1, 4, 14, 68, 362, 2224, 14940, 110348, 878600, 7518002, 68529122, 662709832, 6764329158, 72622813172, 817239648500, 9612724174088, 117878757097178, 1503660164683864, 19911519090176808, 273221610513382028, 3878513600608651636, 56873187579428449852, 860296560100458300892
Offset: 0

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Author

Ilya Gutkovskiy, Mar 22 2018

Keywords

Comments

Exponential transform of A001615.

Examples

			E.g.f.: A(x) = 1 + x/1! + 4*x^2/2! + 14*x^3/3! + 68*x^4/4! + 362*x^5/5! + 2224*x^6/6! + 14940*x^7/7! + ...
		

Crossrefs

Programs

  • Mathematica
    psi[n_] := n Sum[MoebiusMu[d]^2/d, {d, Divisors@n}]; a[n_] := a[n] = SeriesCoefficient[Exp[Sum[psi[k] x^k/k!, {k, 1, n}]], {x, 0, n}]; Table[a[n] n!, {n, 0, 23}]
    psi[n_] := n Sum[MoebiusMu[d]^2/d, {d, Divisors@n}]; a[n_] := a[n] = Sum[psi[k] Binomial[n - 1, k - 1] a[n - k], {k, 1, n}]; a[0] = 1; Table[a[n], {n, 0, 23}]

Formula

E.g.f.: exp(Sum_{k>=1} A001615(k)*x^k/k!).

A306483 Expansion of Product_{k>=1} 1/(1 - psi(k)*x^k), where psi() is the Dedekind psi function (A001615).

Original entry on oeis.org

1, 1, 4, 8, 23, 41, 114, 200, 491, 909, 2036, 3710, 8235, 14743, 31058, 56538, 115435, 207401, 417876, 745578, 1470371, 2626489, 5086108, 9030162, 17347019, 30620651, 58060380, 102426652, 192288399, 337633825, 629845430, 1101958752, 2040109199, 3563507377, 6553539316, 11412799294
Offset: 0

Views

Author

Ilya Gutkovskiy, Feb 18 2019

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 35; CoefficientList[Series[Product[1/(1 - DirichletConvolve[i, MoebiusMu[i]^2, i, k] x^k), {k, 1, nmax}], {x, 0, nmax}], x]
    nmax = 35; CoefficientList[Series[Exp[Sum[Sum[DirichletConvolve[i, MoebiusMu[i]^2, i, j]^k x^(j k)/k, {j, 1, nmax}], {k, 1, nmax}]], {x, 0, nmax}], x]
    a[n_] := a[n] = If[n == 0, 1, Sum[Sum[d DirichletConvolve[i, MoebiusMu[i]^2, i, d]^(k/d), {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 35}]

Formula

G.f.: exp(Sum_{k>=1} Sum_{j>=1} psi(j)^k*x^(j*k)/k).
From Vaclav Kotesovec, Feb 23 2019: (Start)
a(n) ~ c * 3^(n/2), where
c = 84.0923381459819921541124348082985... if n is even and
c = 82.6952907990079575265849718772977... if n is odd. (End)

A381709 Euler transform of n^3 * A065960(n).

Original entry on oeis.org

1, 1, 137, 2351, 29075, 408429, 5957562, 76590384, 955079422, 11831378688, 142650905559, 1668991927795, 19144774189917, 215790313316371, 2388025355854986, 25973791505651972, 278176027053878678, 2936495245822593766, 30573379794788083289, 314185573464039742503
Offset: 0

Views

Author

Seiichi Manyama, Mar 04 2025

Keywords

Crossrefs

Programs

  • PARI
    my(N=20, x='x+O('x^N)); Vec(exp(sum(k=1, N, sigma(k^2, 4)*x^k/k)))

Formula

G.f.: 1/Product_{k>=1} (1 - x^k)^(k^3 * A065960(k)).
G.f.: exp( Sum_{k>=1} sigma_4(k^2) * x^k/k ).
a(0) = 1; a(n) = (1/n) * Sum_{k=1..n} sigma_4(k^2) * a(n-k).

A307073 Expansion of 1/(1 - Sum_{k>=1} mu(k)^2*x^k/(1 - x^k)^2).

Original entry on oeis.org

1, 1, 4, 11, 33, 94, 279, 803, 2348, 6823, 19879, 57834, 168405, 490125, 1426824, 4153197, 12089787, 35191868, 102440785, 298194567, 868017488, 2526715121, 7355031727, 21409798576, 62321907805, 181413177769, 528076639862, 1537181201003, 4474589318797, 13025106833162, 37914855831345
Offset: 0

Views

Author

Ilya Gutkovskiy, Mar 22 2019

Keywords

Comments

Invert transform of A001615.

Crossrefs

Programs

  • Mathematica
    nmax = 30; CoefficientList[Series[1/(1 - Sum[MoebiusMu[k]^2 x^k/(1 - x^k)^2, {k, 1, nmax}]), {x, 0, nmax}], x]
    a[0] = 1; a[n_] := a[n] = Sum[DirichletConvolve[j, MoebiusMu[j]^2, j, k] a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 30}]

Formula

a(0) = 1; a(n) = Sum_{k=1..n} A001615(k)*a(n-k).
Previous Showing 11-14 of 14 results.