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 1-8 of 8 results.

A166861 Euler transform of Fibonacci numbers.

Original entry on oeis.org

1, 1, 2, 4, 8, 15, 30, 56, 108, 203, 384, 716, 1342, 2487, 4614, 8510, 15675, 28749, 52652, 96102, 175110, 318240, 577328, 1045068, 1888581, 3406455, 6134530, 11029036, 19799363, 35490823, 63531134, 113570988, 202767037, 361565865, 643970774, 1145636750
Offset: 0

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Author

Keywords

Comments

In general, the sequence with g.f. Product_{k>=1} 1/(1-x^k)^Fibonacci(k+z), where z is nonnegative integer, is asymptotic to phi^(n + z/4) / (2 * sqrt(Pi) * 5^(1/8) * n^(3/4)) * exp((phi/10 - 1/2) * Fibonacci(z) - Fibonacci(z+1)/10 + 2 * 5^(-1/4) * phi^(z/2) * sqrt(n) + s), where s = Sum_{k>=2} (Fibonacci(z) + Fibonacci(z+1) * phi^k) / ((phi^(2*k) - phi^k - 1)*k) and phi = A001622 = (1+sqrt(5))/2 is the golden ratio. - Vaclav Kotesovec, Aug 06 2015

Examples

			G.f. = 1 + x + 2*x^2 + 4*x^3 + 8*x^4 + 15*x^5 + 30*x^6 + 56*x^7 + 108*x^8 + 203*x^9 + ...
		

Crossrefs

Programs

  • Maple
    F:= proc(n) option remember; (<<1|1>, <1|0>>^n)[1, 2] end:
    a:= proc(n) option remember; `if`(n=0, 1, add(add(d*
          F(d), d=numtheory[divisors](j))*a(n-j), j=1..n)/n)
        end:
    seq(a(n), n=0..40);  # Alois P. Heinz, Jan 12 2017
  • Mathematica
    CoefficientList[Series[Product[1/(1-x^k)^Fibonacci[k], {k, 1, 40}], {x, 0, 40}], x] (* Vaclav Kotesovec, Aug 05 2015 *)
  • PARI
    ET(v)=Vec(prod(k=1,#v,1/(1-x^k+x*O(x^#v))^v[k]))
    ET(vector(40,n,fibonacci(n)))
    
  • SageMath
    def EulerTransform(a):
        @cached_function
        def b(n):
            if n == 0: return 1
            s = sum(sum(d * a(d) for d in divisors(j)) * b(n-j) for j in (1..n))
            return s//n
        return b
    a = BinaryRecurrenceSequence(1, 1)
    b = EulerTransform(a)
    print([b(n) for n in range(36)]) # Peter Luschny, Nov 11 2020

Formula

G.f.: Product_{k>0} 1/(1 - x^k)^Fibonacci(k).
a(n) ~ phi^n / (2 * sqrt(Pi) * 5^(1/8) * n^(3/4)) * exp(-1/10 + 2*5^(-1/4)*sqrt(n) + s), where s = Sum_{k>=2} phi^k / ((phi^(2*k) - phi^k - 1)*k) = 0.600476601392575912969719494850393576083765123939643511355547131467... and phi = A001622 = (1+sqrt(5))/2 is the golden ratio. - Vaclav Kotesovec, Aug 06 2015
G.f.: exp(Sum_{k>=1} x^k/(k*(1 - x^k - x^(2*k)))). - Ilya Gutkovskiy, May 29 2018

Extensions

First formula corrected by Vaclav Kotesovec, Aug 05 2015

A260916 Expansion of Product_{k>=1} ((1+x^k)/(1-x^k))^(Fibonacci(k)).

Original entry on oeis.org

1, 2, 4, 10, 22, 48, 104, 220, 460, 954, 1956, 3976, 8026, 16084, 32032, 63440, 124974, 245008, 478204, 929452, 1799508, 3471396, 6673724, 12788976, 24433528, 46546738, 88432264, 167575474, 316768948, 597389576, 1124092476, 2110661644, 3955006820, 7396477224
Offset: 0

Views

Author

Vaclav Kotesovec, Aug 18 2015

Keywords

Comments

Convolution of A166861 and A261050.

Crossrefs

Programs

  • Mathematica
    nmax = 40; CoefficientList[Series[Product[((1+x^k)/(1-x^k))^Fibonacci[k], {k, 1, nmax}], {x, 0, nmax}], x]

Formula

a(n) ~ phi^n / (2^(3/4) * 5^(1/8) * sqrt(Pi) * n^(3/4)) * exp(-1/5 + 2*5^(-1/4)*sqrt(2*n) + s), where s = 2 * Sum_{k>=1} phi^(2*k+1) / ((phi^(4*k+2) - phi^(2*k+1) - 1)*(2*k+1)) = 0.276751423987223411719438512082359840225908317... and phi = A001622 = (1+sqrt(5))/2 is the golden ratio.

A261051 Expansion of Product_{k>=1} (1+x^k)^(Lucas(k)).

Original entry on oeis.org

1, 1, 3, 7, 14, 33, 69, 148, 307, 642, 1314, 2684, 5432, 10924, 21841, 43431, 85913, 169170, 331675, 647601, 1259737, 2441706, 4716874, 9083215, 17439308, 33387589, 63749174, 121409236, 230658963, 437198116, 826838637, 1560410267, 2938808875, 5524005110
Offset: 0

Views

Author

Vaclav Kotesovec, Aug 08 2015

Keywords

Crossrefs

Programs

  • Maple
    L:= n-> (<<0|1>, <1|1>>^n. <<2, 1>>)[1, 1]:
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
           add(binomial(L(i), j)*b(n-i*j, i-1), j=0..n/i)))
        end:
    a:= n-> b(n$2):
    seq(a(n), n=0..50);  # Alois P. Heinz, Aug 08 2015
  • Mathematica
    nmax=40; CoefficientList[Series[Product[(1+x^k)^LucasL[k],{k,1,nmax}],{x,0,nmax}],x]

Formula

a(n) ~ phi^n / (2*sqrt(Pi)*n^(3/4)) * exp(-1 + 1/(2*sqrt(5)) + 2*sqrt(n) + s), where s = Sum_{k>=2} (-1)^(k+1) * (2 + phi^k)/((phi^(2*k) - phi^k - 1)*k) = -0.590290697526802161885355317939144642488927381134222996704542... and phi = A001622 = (1+sqrt(5))/2 is the golden ratio.
G.f.: exp(Sum_{k>=1} (-1)^(k+1)*x^k*(1 + 2*x^k)/(k*(1 - 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...

A357475 Expansion of Product_{k>=1} 1 / (1 + x^k)^Fibonacci(k).

Original entry on oeis.org

1, -1, 0, -2, 0, -3, 0, -4, 2, -5, 8, 0, 26, 19, 74, 74, 195, 221, 464, 560, 1042, 1258, 2154, 2536, 3997, 4341, 6152, 5204, 5447, -1617, -10790, -39710, -83915, -181639, -336564, -633844, -1108334, -1952371, -3293590, -5568202, -9148916, -15017471, -24144556, -38697396, -61005748, -95708150
Offset: 0

Views

Author

Ilya Gutkovskiy, Oct 02 2022

Keywords

Comments

Convolution inverse of A261050.

Crossrefs

Programs

  • Mathematica
    nmax = 45; CoefficientList[Series[Product[1/(1 + x^k)^Fibonacci[k], {k, 1, nmax}], {x, 0, nmax}], x]
    a[0] = 1; a[n_] := a[n] = (1/n) Sum[Sum[(-1)^(k/d) d Fibonacci[d], {d, Divisors[k]}] a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 45}]

Formula

a(n) = Sum_{k=0..n} (-1)^k * A337009(n,k). - Alois P. Heinz, Apr 30 2023

A357179 Expansion of Product_{k>=1} (1 - x^k)^Fibonacci(k).

Original entry on oeis.org

1, -1, -1, -1, -1, 0, -1, 2, 1, 5, 6, 14, 15, 32, 40, 64, 86, 131, 166, 237, 287, 362, 389, 368, 149, -339, -1477, -3680, -7827, -15245, -28270, -50493, -87886, -149827, -250966, -414542, -675741, -1089267, -1736640, -2741788, -4284837, -6632751, -10162683, -15412613, -23110653, -34236290
Offset: 0

Views

Author

Ilya Gutkovskiy, Oct 02 2022

Keywords

Comments

Convolution inverse of A166861.

Crossrefs

Programs

  • Mathematica
    nmax = 45; CoefficientList[Series[Product[(1 - x^k)^Fibonacci[k], {k, 1, nmax}], {x, 0, nmax}], x]
    a[0] = 1; a[n_] := a[n] = -(1/n) Sum[Sum[d Fibonacci[d], {d, Divisors[k]}] a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 45}]

A291650 Expansion of Product_{k>=2} (1 + x^Fibonacci(k))^Fibonacci(k).

Original entry on oeis.org

1, 1, 2, 5, 4, 12, 14, 16, 42, 35, 65, 100, 84, 205, 201, 254, 490, 386, 749, 917, 851, 1816, 1566, 2260, 3513, 2784, 5566, 5748, 6116, 11366, 9048, 14740, 19037, 16095, 31576, 28505, 35218, 56334, 43671, 77512, 85163, 80577, 147756, 121016, 172408, 236022
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 28 2017

Keywords

Comments

Number of partitions of n into distinct Fibonacci parts (1 counted as single Fibonacci number), where Fibonacci(k) different parts of size Fibonacci(k) are available (1a, 2a, 2b, 3a, 3b, 3c, ...).

Examples

			a(3) = 5 because we have [3a], [3b], [3c], [2a, 1a] and [2b, 1a].
		

Crossrefs

Programs

  • Mathematica
    nmax = 50; CoefficientList[Series[Product[(1 + x^Fibonacci[k])^Fibonacci[k], {k, 2, nmax}], {x, 0, nmax}], x]

Formula

G.f.: Product_{k>=2} (1 + x^A000045(k))^A000045(k).
Showing 1-8 of 8 results.