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 1-5 of 5 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

A337009 Triangle of the Multiset Transform of the Fibonacci Sequence.

Original entry on oeis.org

1, 1, 1, 2, 1, 1, 3, 3, 1, 1, 5, 5, 3, 1, 1, 8, 11, 6, 3, 1, 1, 13, 19, 13, 6, 3, 1, 1, 21, 37, 25, 14, 6, 3, 1, 1, 34, 65, 52, 27, 14, 6, 3, 1, 1, 55, 120, 98, 58, 28, 14, 6, 3, 1, 1, 89, 210, 191, 113, 60, 28, 14, 6, 3, 1, 1, 144, 376, 360, 229, 119, 61, 28, 14, 6, 3, 1, 1, 233, 654, 678, 443, 244, 121, 61, 28, 14, 6, 3, 1, 1
Offset: 1

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Author

R. J. Mathar, Aug 11 2020

Keywords

Comments

Short definition of the Multiset Transformation: supposed we have F(w) distinct objects of weight w. Then T(n,k) is the number of bags of objects with total weight n containing k objects. Multisets means that objects may appear more than once in the bag, but the order of the objects in the bag does not matter.
Apparently A200544 is the limit of the reversed rows as n approaches infinity.

Examples

			The triangle starts with rows n>=1 and columns k>=1:
    1
    1     1
    2     1     1
    3     3     1     1
    5     5     3     1     1
    8    11     6     3     1     1
   13    19    13     6     3     1     1
   21    37    25    14     6     3     1     1
   34    65    52    27    14     6     3     1     1
   55   120    98    58    28    14     6     3     1     1
   89   210   191   113    60    28    14     6     3     1     1
  144   376   360   229   119    61    28    14     6     3     1     1
  233   654   678   443   244   121    61    28    14     6     3     1     1
  377  1149  1255   866   481   250   122    61    28    14     6     3     1  1
  ...
		

Crossrefs

Cf. A000045 (column k=1), A089098 (column k=2), A166861 (row sums), A200544 (limiting row?), A357475.

Programs

  • Maple
    F:= proc(n) option remember; (<<1|1>, <1|0>>^n)[1, 2] end:
    b:= proc(n, i) option remember; expand(`if`(n=0 or i=1, x^n,
          add(binomial(F(i)+j-1, j)*b(n-i*j, i-1)*x^j, j=0..n/i)))
        end:
    T:= n-> (p-> seq(coeff(p, x, i), i=1..n))(b(n$2)):
    seq(T(n), n=1..12);  # Alois P. Heinz, Oct 29 2021
  • Mathematica
    nn = 13;
    Rest@CoefficientList[#, y]& /@ (Series[Product[1/(1 - y x^i)^Fibonacci[i], {i, 1, nn}], {x, 0, nn}] // Rest@CoefficientList[#, x]&) // Flatten (* Jean-François Alcover, Oct 29 2021 *)

Formula

G.f.: Product_{j>=1} 1/(1-y*x^j)^Fibonacci(j). - Jean-François Alcover, Oct 29 2021
Sum_{k=0..n} (-1)^k * T(n,k) = A357475(n). - Alois P. Heinz, Apr 30 2023

A358369 Euler transform of 2^floor(n/2), (A016116).

Original entry on oeis.org

1, 1, 3, 5, 12, 20, 43, 73, 146, 250, 475, 813, 1499, 2555, 4592, 7800, 13761, 23253, 40421, 67963, 116723, 195291, 332026, 552882, 932023, 1544943, 2585243, 4267081, 7094593, 11662769, 19281018, 31575874, 51937608, 84753396, 138772038, 225693778, 368017636
Offset: 0

Views

Author

Peter Luschny, Nov 17 2022

Keywords

Crossrefs

Sequences that can be represented as a EulerTransform(BinaryRecurrenceSequence()) include A000009, A000041, A000712, A001970, A002513, A010054, A015128, A022567, A034691, A111317, A111335, A117410, A156224, A166861, A200544, A261031, A261329, A358449.

Programs

  • Maple
    BinaryRecurrenceSequence := proc(b, c, u0:=0, u1:=1) local u;
    u := proc(n) option remember; if n < 2 then return [u0, u1][n + 1] fi;
    b*u(n - 1) + c*u(n - 2) end; u end:
    EulerTransform := proc(a) local b;
    b := proc(n) option remember; if n = 0 then return 1 fi; add(add(d * a(d),
    d = NumberTheory:-Divisors(j)) * b(n-j), j = 1..n) / n end; b end:
    a := EulerTransform(BinaryRecurrenceSequence(0, 2, 1)): seq(a(n), n=0..36);
  • Python
    from typing import Callable
    from functools import cache
    from sympy import divisors
    def BinaryRecurrenceSequence(b:int, c:int, u0:int=0, u1:int=1) -> Callable:
        @cache
        def u(n: int) -> int:
            if n < 2:
                return [u0, u1][n]
            return b * u(n - 1) + c * u(n - 2)
        return u
    def EulerTransform(a: Callable) -> Callable:
        @cache
        def b(n: int) -> int:
            if n == 0:
                return 1
            s = sum(sum(d * a(d) for d in divisors(j)) * b(n - j)
                for j in range(1, n + 1))
            return s // n
        return b
    b = BinaryRecurrenceSequence(0, 2, 1)
    a = EulerTransform(b)
    print([a(n) for n in range(37)])
  • Sage
    # uses[EulerTransform from A166861]
    b = BinaryRecurrenceSequence(0, 2, 1)
    a = EulerTransform(b)
    print([a(n) for n in range(37)])
    

A260787 G.f.: Product_{k>=1} 1/(1-x^k)^Fibonacci(k+2).

Original entry on oeis.org

1, 2, 6, 15, 38, 89, 210, 474, 1065, 2339, 5091, 10919, 23230, 48887, 102126, 211599, 435561, 890617, 1810786, 3661118, 7365473, 14747049, 29397160, 58356179, 115392801, 227332038, 446304671, 873298579, 1703463864, 3312873935, 6424553973, 12425158365, 23968214357, 46120280910, 88535346223
Offset: 0

Views

Author

N. J. A. Sloane, Aug 05 2015

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

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[Product[1/(1-x^k)^Fibonacci[k+2], {k, 1, 20}], {x, 0, 20}], x] (* Vaclav Kotesovec, Aug 05 2015 *)

Formula

a(n) ~ phi^(n+1/2) / (2 * sqrt(Pi) * 5^(1/8) * n^(3/4)) * exp(phi/10 - 7/10 + 2*5^(-1/4)*phi*sqrt(n) + s), where s = Sum_{k>=2} (1 + 2*phi^k) / ((phi^(2*k) - phi^k - 1)*k) = 1.39069800276768443926918973402733105305129194986259856042723... and phi = A001622 = (1+sqrt(5))/2 is the golden ratio. - Vaclav Kotesovec, Aug 06 2015

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 1-5 of 5 results.