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 1-4 of 4 results.

A304494 Expansion of e.g.f. Product_{k>=1} (1 + x^k)^H(k), where H(k) is the k-th harmonic number.

Original entry on oeis.org

1, 1, 3, 20, 103, 899, 8143, 84678, 975049, 13082993, 186340631, 2878977408, 48899305783, 876721463435, 16971889682707, 349059348881834, 7565120836998801, 173313418321443809, 4197655086606145387, 106097089652021765356, 2816940203630838490791, 78147038018470085005235
Offset: 0

Views

Author

Ilya Gutkovskiy, May 13 2018

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 21; CoefficientList[Series[Product[(1 + x^k)^HarmonicNumber[k], {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
    a[n_] := a[n] = If[n == 0, 1, Sum[Sum[(-1)^(k/d + 1) d HarmonicNumber[d], {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[n! a[n], {n, 0, 21}]

Formula

E.g.f.: Product_{k>=1} (1 + x^k)^(A001008(k)/A002805(k)).

A305201 Expansion of e.g.f. Product_{k>=1} 1/(1 - H(k)*x^k), where H(k) is the k-th harmonic number.

Original entry on oeis.org

1, 1, 5, 26, 208, 1644, 18728, 201466, 2809672, 39505800, 647509992, 10851033984, 210456343392, 4090234000800, 89123794754304, 2000019423403824, 48674645933985408, 1217362548455301504, 32913123947574009984, 910006995701419453440, 26898048642355515339264
Offset: 0

Views

Author

Ilya Gutkovskiy, May 27 2018

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 20; CoefficientList[Series[Product[1/(1 - HarmonicNumber[k] x^k), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
    nmax = 20; CoefficientList[Series[Exp[Sum[Sum[HarmonicNumber[j]^k x^(j k)/k, {j, 1, nmax}], {k, 1, nmax}]], {x, 0, nmax}], x] Range[0, nmax]!
    a[n_] := a[n] = If[n == 0, 1, Sum[Sum[d HarmonicNumber[d]^(k/d), {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[n! a[n], {n, 0, 20}]

Formula

E.g.f.: Product_{k>=1} 1/(1 - (A001008(k)/A002805(k))*x^k).
E.g.f.: exp(Sum_{k>=1} Sum_{j>=1} H(j)^k*x^(j*k)/k).
a(n) ~ n! * c * (3/2)^(n/2 + 1) / (3 - sqrt(6)), where c = Product_{k>=3} 1/(1 - (2/3)^(k/2) * H(k)) = 20723937.5142714953478411012151498609843924051679047516... - Vaclav Kotesovec, Nov 05 2019

A304496 Expansion of e.g.f. Product_{k>=1} (1 - x^k)^H(k), where H(k) is the k-th harmonic number.

Original entry on oeis.org

1, -1, -3, -2, 3, 261, 745, 12412, 16289, -260081, -5424199, -96985734, -2047127621, -17402659299, -84365982987, -2937186832544, 39650368238977, 1047895936025183, 35975009604881845, 638531451763185398, 14668256344792565331, 248159858571597211093, 6320237684944085611809
Offset: 0

Views

Author

Ilya Gutkovskiy, May 13 2018

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 22; CoefficientList[Series[Product[(1 - x^k)^HarmonicNumber[k], {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
    a[n_] := a[n] = If[n == 0, 1, Sum[-Sum[d HarmonicNumber[d], {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[n! a[n], {n, 0, 22}]

Formula

E.g.f.: Product_{k>=1} (1 - x^k)^(A001008(k)/A002805(k)).

A305128 Expansion of e.g.f. Product_{k>=1} 1/(1 - x^k)^AH(k), where AH(k) is the k-th alternating harmonic number.

Original entry on oeis.org

1, 1, 3, 14, 79, 539, 4663, 42468, 457945, 5433281, 71036231, 994289658, 15544425103, 253283689619, 4489180389835, 84521336758904, 1687130833152561, 35365641206048129, 790065486354237643, 18340253632236738022, 449655289227002010351, 11492300073384698090795, 306803167368168113022271
Offset: 0

Views

Author

Ilya Gutkovskiy, May 26 2018

Keywords

Comments

a(n)/n! is the Euler transform of [1, 1 - 1/2, 1 - 1/2 + 1/3, 1 - 1/2 + 1/3 - 1/4, 1 - 1/2 + 1/3 - 1/4 + 1/5, ...].

Crossrefs

Programs

  • Mathematica
    nmax = 22; CoefficientList[Series[Product[1/(1 - x^k)^Sum[(-1)^(j + 1)/j, {j, 1, k}], {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
    a[n_] := a[n] = If[n == 0, 1, Sum[Sum[d ((-1)^(d + 1) LerchPhi[-1, 1, d + 1] + Log[2]), {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[n! a[n], {n, 0, 22}]

Formula

E.g.f.: Product_{k>=1} 1/(1 - x^k)^(A058313(k)/A058312(k)).
Showing 1-4 of 4 results.