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.

A261329 Euler transform of Pell numbers.

Original entry on oeis.org

1, 1, 3, 8, 23, 62, 175, 477, 1319, 3602, 9851, 26779, 72726, 196724, 531157, 1430144, 3842911, 10303055, 27570786, 73637306, 196333303, 522584286, 1388786089, 3685169795, 9764703347, 25838430572, 68282175170, 180221449469, 475102410065, 1251038486529
Offset: 0

Views

Author

Vaclav Kotesovec, Aug 15 2015

Keywords

Crossrefs

Programs

  • Mathematica
    nmax=40; Pell[0]=0; Pell[1]=1; Pell[n_]:=Pell[n] = 2*Pell[n-1] + Pell[n-2]; CoefficientList[Series[Product[1/(1-x^k)^Pell[k], {k, 1, nmax}], {x, 0, nmax}], x]
  • SageMath
    # uses[EulerTransform from A166861]
    a = BinaryRecurrenceSequence(2, 1)
    b = EulerTransform(a)
    print([b(n) for n in range(30)]) # Peter Luschny, Nov 11 2020

Formula

G.f.: Product_{k>=1} 1/(1-x^k)^(A000129(k)).
a(n) ~ (1+sqrt(2))^n * exp(-1/8 + 2^(1/4)*sqrt(n) + s) / (2^(11/8) * sqrt(Pi) * n^(3/4)), where s = Sum_{k>=2} 1/(((sqrt(2)+1)^k - (sqrt(2)-1)^k - 2)*k) = 0.17615706029370539578355193664752741450665073523628663099586621933373...
G.f.: exp(Sum_{k>=1} x^k/(k*(1 - 2*x^k - x^(2*k)))). - Ilya Gutkovskiy, May 30 2018

A261331 Expansion of Product_{k>=1} (1+x^k)^(A000129(k)).

Original entry on oeis.org

1, 1, 2, 7, 18, 52, 143, 396, 1083, 2971, 8087, 21981, 59533, 160857, 433467, 1165542, 3126951, 8372451, 22374172, 59684669, 158941356, 422582925, 1121814072, 2973703449, 7871754065, 20809918535, 54943916547, 144891525408, 381647503607, 1004149670985
Offset: 0

Views

Author

Vaclav Kotesovec, Aug 15 2015

Keywords

Crossrefs

Programs

  • Mathematica
    nmax=40; Pell[0]=0; Pell[1]=1; Pell[n_]:=Pell[n] = 2*Pell[n-1] + Pell[n-2]; CoefficientList[Series[Product[(1+x^k)^Pell[k], {k, 1, nmax}], {x, 0, nmax}], x]

Formula

a(n) ~ (1+sqrt(2))^n * exp(-1/8 + 2^(1/4)*sqrt(n) + s) / (2^(11/8) * sqrt(Pi) * n^(3/4)), where s = Sum_{k>=2} (-1)^(k+1)/(((sqrt(2)+1)^k - (sqrt(2)-1)^k - 2)*k) = -0.1149083344289588668149210160138124159112948627968378825745674888...
G.f.: exp(Sum_{k>=1} (-1)^(k+1)*x^k/(k*(1 - 2*x^k - x^(2*k)))). - Ilya Gutkovskiy, May 30 2018

A261332 Expansion of Product_{k>=1} (1+x^k)^(A002203(k)).

Original entry on oeis.org

1, 2, 7, 26, 83, 278, 894, 2848, 8947, 27844, 85774, 262090, 794802, 2393874, 7165622, 21327412, 63146545, 186063052, 545783103, 1594268778, 4638773567, 13447773510, 38850645513, 111874844146, 321166890522, 919314145044, 2624198013317, 7471158542418
Offset: 0

Views

Author

Vaclav Kotesovec, Aug 15 2015

Keywords

Crossrefs

Programs

  • Mathematica
    nmax=40; cPell[0]=2; cPell[1]=2; cPell[n_]:=cPell[n] = 2*cPell[n-1] + cPell[n-2]; CoefficientList[Series[Product[(1+x^k)^cPell[k], {k, 1, nmax}], {x, 0, nmax}], x]

Formula

a(n) ~ (1+sqrt(2))^n * exp(-1 + 2^(-3/2) + 2*sqrt(n) + s) / (2 * sqrt(Pi) * n^(3/4)), where s = Sum_{k>=2} = 2*(-1)^(k+1)/(((1+sqrt(2))^k + 2/(1 + (1+sqrt(2))^k) - 3)*k) = -0.2731939535370496116124191192900280854879921353977...
Showing 1-3 of 3 results.