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 1-9 of 9 results.

A218482 First differences of the binomial transform of the partition numbers (A000041).

Original entry on oeis.org

1, 1, 3, 8, 21, 54, 137, 344, 856, 2113, 5179, 12614, 30548, 73595, 176455, 421215, 1001388, 2371678, 5597245, 13166069, 30873728, 72185937, 168313391, 391428622, 908058205, 2101629502, 4853215947, 11183551059, 25718677187, 59030344851, 135237134812, 309274516740
Offset: 0

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Author

Paul D. Hanna, Oct 29 2012

Keywords

Comments

a(n) = A103446(n) for n>=1; here a(0) is set to 1 in accordance with the definition and other important generating functions.
From Gus Wiseman, Dec 12 2022: (Start)
Also the number of sequences of compositions (A133494) with weakly decreasing lengths and total sum n. For example, the a(0) = 1 through a(3) = 8 sequences are:
() ((1)) ((2)) ((3))
((11)) ((12))
((1)(1)) ((21))
((111))
((1)(2))
((2)(1))
((11)(1))
((1)(1)(1))
The case of constant lengths is A101509.
The case of strictly decreasing lengths is A129519.
The case of sequences of partitions is A141199.
The case of twice-partitions is A358831.
(End)

Examples

			G.f.: A(x) = 1 + x + 3*x^2 + 8*x^3 + 21*x^4 + 54*x^5 + 137*x^6 + 344*x^7 +...
The g.f. equals the product:
A(x) = (1-x)/((1-x)-x) * (1-x)^2/((1-x)^2-x^2) * (1-x)^3/((1-x)^3-x^3) * (1-x)^4/((1-x)^4-x^4) * (1-x)^5/((1-x)^5-x^5) * (1-x)^6/((1-x)^6-x^6) * (1-x)^7/((1-x)^7-x^7) *...
and also equals the series:
A(x) = 1  +  x*(1-x)/((1-x)-x)^2  +  x^4*(1-x)^2/(((1-x)-x)*((1-x)^2-x^2))^2  +  x^9*(1-x)^3/(((1-x)-x)*((1-x)^2-x^2)*((1-x)^3-x^3))^2  +  x^16*(1-x)^4/(((1-x)-x)*((1-x)^2-x^2)*((1-x)^3-x^3)*((1-x)^4-x^4))^2 +...
		

Crossrefs

Programs

  • Maple
    b:= proc(n) option remember;
          add(combinat[numbpart](k)*binomial(n,k), k=0..n)
        end:
    a:= n-> b(n)-b(n-1):
    seq(a(n), n=0..50);  # Alois P. Heinz, Aug 19 2014
  • Mathematica
    Flatten[{1, Table[Sum[Binomial[n-1,k]*PartitionsP[k+1],{k,0,n-1}],{n,1,30}]}] (* Vaclav Kotesovec, Jun 25 2015 *)
  • PARI
    {a(n)=sum(k=0,n,(binomial(n,k)-if(n>0,binomial(n-1,k)))*numbpart(k))}
    for(n=0,40,print1(a(n),", "))
    
  • PARI
    {a(n)=local(X=x+x*O(x^n));polcoeff(prod(k=1,n,(1-x)^k/((1-x)^k-X^k)),n)}
    
  • PARI
    {a(n)=local(X=x+x*O(x^n));polcoeff(sum(m=0,n,x^m*(1-x)^(m*(m-1)/2)/prod(k=1,m,((1-x)^k - X^k))),n)}
    
  • PARI
    {a(n)=local(X=x+x*O(x^n));polcoeff(sum(m=0,n,x^(m^2)*(1-X)^m/prod(k=1,m,((1-x)^k - x^k)^2)),n)}
    
  • PARI
    {a(n)=local(X=x+x*O(x^n));polcoeff(exp(sum(m=1,n+1,x^m/((1-x)^m-X^m)/m)),n)}
    
  • PARI
    {a(n)=local(X=x+x*O(x^n));polcoeff(exp(sum(m=1,n+1,sigma(m)*x^m/(1-X)^m/m)),n)}
    
  • PARI
    {a(n)=local(X=x+x*O(x^n));polcoeff(prod(k=1,n,(1 + x^k/(1-X)^k)^valuation(2*k,2)),n)}

Formula

G.f.: Product_{n>=1} (1-x)^n / ((1-x)^n - x^n).
G.f.: Sum_{n>=0} x^n * (1-x)^(n*(n-1)/2) / Product_{k=1..n} ((1-x)^k - x^k).
G.f.: Sum_{n>=0} x^(n^2) * (1-x)^n / Product_{k=1..n} ((1-x)^k - x^k)^2.
G.f.: exp( Sum_{n>=1} x^n/((1-x)^n - x^n) / n ).
G.f.: exp( Sum_{n>=1} sigma(n) * x^n/(1-x)^n / n ), where sigma(n) is the sum of divisors of n (A000203).
G.f.: Product_{n>=1} (1 + x^n/(1-x)^n)^A001511(n), where 2^A001511(n) is the highest power of 2 that divides 2*n.
a(n) ~ exp(Pi*sqrt(n/3) + Pi^2/24) * 2^(n-2) / (n*sqrt(3)). - Vaclav Kotesovec, Jun 25 2015

A025168 Expansion of e.g.f.: exp(x/(1-2*x)).

Original entry on oeis.org

1, 1, 5, 37, 361, 4361, 62701, 1044205, 19748177, 417787921, 9770678101, 250194150581, 6959638411705, 208919770666777, 6729933476435261, 231512615111396221, 8469125401589550241, 328241040596380393505, 13434223364220816489637, 578931271898150002093381
Offset: 0

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Author

Keywords

Comments

From Peter Bala, Nov 21 2017: (Start)
The sequence terms have the form 4*m + 1 (follows from the recurrence).
For k = 2,3,4,... the difference a(n+k) - a(n) is divisible by k (proof by induction on n making use of the recurrence - the starting case a(k) == a(0) (mod k) for all k follows from the sum formula for a(k)). Hence for each k, the sequence b(n) == a(n) (mod k) is periodic with the exact period dividing k. (End)
Compound Poisson distribution with parameter 1 and distribution Geometric(1/2) has a probability mass function p_n = a(n)*e^(-1/2)/(4^n*n!). More specifically, let S = Sum_{i=0..N} X_i where X_i's are i.i.d. random variables with Geometric(1/2) distribution (i.e., Pr{X_i = k} = 1/2^(k+1) for k=0,1,2...) and N is a random variable with Poisson(1) distribution independent of all X_i's. Then Pr{S=n} = a(n)*e^(-1/2)/(4^n*n!) = a(n)*e^(-1/2)/A047053(n) for nonnegative integers n. - Xiaohan Zhang, Nov 16 2022

Crossrefs

Programs

  • Maple
    with(combstruct); SetSeqSeqL := [T, {T=Set(S), S=Sequence(U,card >= 1), U=Sequence(Z,card >=1)},labeled];
    f:= gfun:-rectoproc({a(n) = (4*n-3)*a(n-1) - 4*(n-2)*(n-1)*a(n-2),a(0)=1,a(1)=1},a(n),remember):
    map(f, [$0..30]); # Robert Israel, Nov 21 2017
  • Mathematica
    Table[ n! 2^n LaguerreL[ n, 1, -1/2 ], {n, 0, 12} ]
    With[{nn=20},CoefficientList[Series[Exp[x/(1-2x)],{x,0,nn}],x] Range[0,nn]!] (* Harvey P. Dale, Aug 12 2012 *)
  • Sage
    A025168 = lambda n: hypergeometric([-n,-n+1], [], 2)
    [Integer(A025168(n).n(100)) for n in range(20)] # Peter Luschny, Sep 22 2014

Formula

Second LAH transform of A000012. LAH transform of A000262. a(n) = Sum_{k=0..n} 2^(n-k)*n!/k!*binomial(n-1, k-1). - Vladeta Jovovic, Oct 17 2003
Define f_1(x), f_2(x), ... such that f_1(x) = e^x, f_{n+1}(x) = (d/dx)(x^2*f_n(x)), for n=2,3,.... Then a(n) = e^(-1/2)*4*(n-1)*f_n(1/2). - Milan Janjic, May 30 2008
From Vaclav Kotesovec, Jun 22 2013: (Start)
D-finite with recurrence: a(n) = (4*n-3)*a(n-1) - 4*(n-2)*(n-1)*a(n-2).
a(n) ~ 2^(n-3/4)*n^(n-1/4)*exp(sqrt(2*n)-n-1/4) * (1-1/(3*sqrt(2*n))).
(End)
E.g.f.: E(0)/2, where E(k) = 1 + 1/(1 - x/(x + (k+1)*(1-2*x)/E(k+1) )); (continued fraction). - Sergei N. Gladkovskii, Jul 09 2013
a(n) = hypergeometric([-n,-n+1],[],2). - Peter Luschny, Sep 22 2014
Sum_{n>=0} a(n)/(4^n*n!) = sqrt(e) = A019774. -Xiaohan Zhang, Nov 16 2022

Extensions

Corrected and extended by Vladeta Jovovic, Sep 08 2002

A320590 Expansion of Product_{k>=1} 1/(1 - x^k/(1 + x)^k).

Original entry on oeis.org

1, 1, 1, 0, 1, -2, 5, -12, 28, -63, 137, -290, 604, -1253, 2617, -5537, 11870, -25666, 55617, -120103, 257582, -548119, 1158437, -2437114, 5117165, -10748530, 22621055, -47728657, 100932549, -213750621, 452855190, -958925784, 2028187595, -4283531490, 9033779224
Offset: 0

Views

Author

Ilya Gutkovskiy, Oct 16 2018

Keywords

Comments

The zero-based binomial transform of this sequence is A000070, and if we remove first terms it becomes A000041.

Crossrefs

Row n=1 of A175804 (except first term). Row n=0 is A281425.
The version for strict partitions is A320591, row n=1 of A378622, first column A293467.
A000009 counts strict integer partitions, differences A087897, A378972.
A000041 counts integer partitions, differences A002865.

Programs

  • Magma
    m:=50; R:=PowerSeriesRing(Rationals(), m); Coefficients(R! ( (&*[1/(1 - x^k/(1 + x)^k): k in [1..(m+2)]]) )); // G. C. Greubel, Oct 29 2018
  • Maple
    seq(coeff(series(mul(1/(1-x^k/(1+x)^k),k=1..n),x,n+1), x, n), n = 0 .. 35); # Muniru A Asiru, Oct 16 2018
  • Mathematica
    nmax = 34; CoefficientList[Series[Product[1/(1 - x^k/(1 + x)^k), {k, 1, nmax}], {x, 0, nmax}], x]
    nmax = 34; CoefficientList[Series[Exp[Sum[DivisorSigma[1, k] x^k/(k (1 + x)^k), {k, 1, nmax}]], {x, 0, nmax}], x]
  • PARI
    m=50; x='x+O('x^m); Vec(prod(k=1, m+2, 1/(1 - x^k/(1 + x)^k))) \\ G. C. Greubel, Oct 29 2018
    

Formula

G.f.: exp(Sum_{k>=1} x^k/(k*((1 + x)^k - x^k))).
G.f.: exp(Sum_{k>=1} sigma(k)*x^k/(k*(1 + x)^k)).

A185003 a(n) = Sum_{k=1..n} binomial(n,k)*sigma(k).

Original entry on oeis.org

1, 5, 16, 45, 116, 284, 673, 1557, 3535, 7910, 17502, 38376, 83500, 180479, 387881, 829605, 1766998, 3749765, 7931114, 16724870, 35173777, 73794660, 154485527, 322771344, 673155141, 1401536934, 2913490375, 6047714599, 12536770558, 25956242579, 53678385266
Offset: 1

Views

Author

Paul D. Hanna, Feb 04 2012

Keywords

Examples

			L.g.f.: L(x) = x + 5*x^2/2 + 16*x^3/3 + 45*x^4/4 + 116*x^5/5 + 284*x^6/6 +...
where exponentiation yields A103446 (with offset=0):
exp(L(x)) = 1 + x + 3*x^2 + 8*x^3 + 21*x^4 + 54*x^5 + 137*x^6 + 344*x^7 +...
		

Crossrefs

Programs

  • Magma
    [&+[Binomial(n,k)*DivisorSigma(1,k):k in [1..n]]:n in [1..31]]; // Marius A. Burtea, Nov 12 2019
    
  • Magma
    [&+[&+[i*Binomial(n,i*j):j in [1..n]]:i in [1..n]]:n in [1..31]]; // Marius A. Burtea, Nov 12 2019
  • Maple
    with(numtheory): seq(add(binomial(n,i)*sigma(i), i=1..n), n=1..40); # Ridouane Oudra, Nov 12 2019
  • Mathematica
    Table[Sum[Binomial[n, k] DivisorSigma[1, k], {k, n}], {n,50}] (* G. C. Greubel, Jun 03 2017 *)
  • PARI
    {a(n)=sum(k=1,n,sigma(k)*binomial(n,k))}
    for(n=1,30,print1(a(n),", "))
    
  • PARI
    {a(n)=local(X=x+x*O(x^n)); n*polcoeff(sum(m=1, n+1, x^m/((1-x)^m-X^m)/m), n)}
    
  • PARI
    {a(n)=local(X=x+x*O(x^n)); n*polcoeff(sum(k=1, n, k*log(1-X)-log((1-x)^k-X^k)), n)}
    
  • PARI
    {a(n)=local(X=x+x*O(x^n)); n*polcoeff(sum(m=1, n+1, sigma(m)*x^m/(1-X)^m/m), n)}
    
  • PARI
    {a(n)=local(X=x+x*O(x^n)); n*polcoeff(sum(k=1, n, valuation(2*k, 2)*log(1 + x^k/(1-X)^k)), n)}
    

Formula

Logarithmic derivative of A103446 (with offset=0), which describes the binomial transform of partitions.
From Paul D. Hanna, Jun 01 2013: (Start)
L.g.f.: Sum_{n>=1} sigma(n) * x^n/(1-x)^n / n.
L.g.f.: Sum_{n>=1} x^n/((1-x)^n - x^n) / n.
L.g.f.: Sum_{n>=1} n*log(1-x) - log((1-x)^n - x^n).
L.g.f.: Sum_{n>=1} A001511(n) * log(1 + x^n/(1-x)^n), where 2^A001511(n) is the highest power of 2 that divides 2*n.
a(n) = A222115(n) - 1. (End)
a(n) ~ Pi^2/12 * n * 2^n. - Vaclav Kotesovec, Dec 30 2015
a(n) = Sum_{i=1..n} Sum_{j=1..n} i*binomial(n,i*j). - Ridouane Oudra, Nov 12 2019

A320591 Expansion of Product_{k>=1} (1 + x^k/(1 + x)^k).

Original entry on oeis.org

1, 1, 0, 1, -2, 4, -7, 11, -16, 23, -36, 65, -129, 256, -473, 772, -1028, 835, 776, -5755, 17562, -41750, 86678, -165145, 299949, -541837, 1020029, -2068203, 4509512, -10252952, 23465297, -52762788, 115160832, -243018459, 496094524, -982431070, 1894710043, -3574095362
Offset: 0

Views

Author

Ilya Gutkovskiy, Oct 16 2018

Keywords

Comments

After the first term, this is the second term of the n-th differences of A000009, or column n=1 of A378622. - Gus Wiseman, Feb 03 2025

Crossrefs

The version for non-strict partitions is A320590, row n=1 of A175804.
Column n=1 (except first term) of A378622. See also A293467, A377285, A378970, A378971, A380412 (column n=0).
A000009 counts strict integer partitions, differences A087897, A378972.
A266232 gives zero-based binomial transform of strict partitions, differences A129519.

Programs

  • Magma
    m:=50; R:=PowerSeriesRing(Rationals(), m); Coefficients(R! ( (&*[(1 + x^k/(1 + x)^k): k in [1..(m+2)]]) )); // G. C. Greubel, Oct 29 2018
  • Maple
    seq(coeff(series(mul((1+x^k/(1+x)^k),k=1..n),x,n+1), x, n), n = 0 .. 37); # Muniru A Asiru, Oct 16 2018
  • Mathematica
    nmax = 37; CoefficientList[Series[Product[(1 + x^k/(1 + x)^k), {k, 1, nmax}], {x, 0, nmax}], x]
    nmax = 37; CoefficientList[Series[Exp[Sum[Sum[(-1)^(k/d + 1) d, {d, Divisors[k]}] x^k/(k (1 + x)^k), {k, 1, nmax}]], {x, 0, nmax}], x]
    Prepend[Table[Differences[PartitionsQ/@Range[0,k+1],k][[2]],{k,0,30}],1] (* Gus Wiseman, Jan 29 2025 *)
  • PARI
    m=50; x='x+O('x^m); Vec(prod(k=1, m+2, (1 + x^k/(1 + x)^k))) \\ G. C. Greubel, Oct 29 2018
    

Formula

G.f.: exp(Sum_{k>=1} (-1)^(k+1)*x^k/(k*((1 + x)^k - x^k))).
G.f.: exp(Sum_{k>=1} A000593(k)*x^k/(k*(1 + x)^k)).
From Peter Bala, Dec 22 2020: (Start)
O.g.f.: Sum_{n >= 0} x^(n*(n+1)/2)/Product_{k = 1..n} ((1 + x)^k - x^k). Cf. A307548.
Conjectural o.g.f.: (1/2) * Sum_{n >= 0} x^(n*(n-1)/2)*(1 + x)^n/( Product_{k = 1..n} ( (1 + x)^k - x^k ) ). (End)
a(n+1) = Sum_{k=0..n} (-1)^(n-k) binomial(n,k) A000009(k+1). - Gus Wiseman, Feb 03 2025

A320563 Expansion of Product_{k>=1} 1/(1 - x^k/(1 - x)^k)^k.

Original entry on oeis.org

1, 1, 4, 13, 41, 125, 374, 1103, 3213, 9259, 26430, 74806, 210095, 585890, 1623240, 4470232, 12241799, 33349751, 90410255, 243977941, 655553258, 1754265279, 4676358086, 12420299846, 32873598566, 86721264126, 228051843891, 597905347237, 1563071037798, 4074973824099
Offset: 0

Views

Author

Ilya Gutkovskiy, Oct 15 2018

Keywords

Comments

First differences of the binomial transform of A000219.

Crossrefs

Programs

  • Maple
    seq(coeff(series(mul((1-x^k/(1-x)^k)^(-k),k=1..n),x,n+1), x, n), n = 0 .. 29); # Muniru A Asiru, Oct 15 2018
  • Mathematica
    nmax = 29; CoefficientList[Series[Product[1/(1 - x^k/(1 - x)^k)^k, {k, 1, nmax}], {x, 0, nmax}], x]
    nmax = 29; CoefficientList[Series[Exp[Sum[DivisorSigma[2, k] x^k/(k (1 - x)^k), {k, 1, nmax}]], {x, 0, nmax}], x]

Formula

G.f.: exp(Sum_{k>=1} sigma_2(k)*x^k/(k*(1 - x)^k)).
a(n) ~ Zeta(3)^(7/36) * 2^(n - 11/18) * exp(3*Zeta(3)^(1/3) * n^(2/3) / 2^(4/3) + Zeta(3)^(2/3) * n^(1/3) / 2^(5/3) + (1 - Zeta(3))/12) / (A * sqrt(3*Pi) * n^(25/36)), where A is the Glaisher-Kinkelin constant A074962. - Vaclav Kotesovec, Oct 15 2018

A307310 Expansion of Product_{k>=1} (1 - x^k/(1 - x)^k).

Original entry on oeis.org

1, -1, -2, -3, -4, -4, -1, 9, 34, 89, 200, 409, 779, 1394, 2339, 3624, 4974, 5323, 1682, -13279, -56222, -163136, -408768, -943275, -2059237, -4310179, -8712425, -17072901, -32486302, -60006278, -107341413, -184979170, -303998680, -467127625, -642495990, -696247140
Offset: 0

Views

Author

Ilya Gutkovskiy, Apr 02 2019

Keywords

Comments

First differences of the binomial transform of A010815.
Convolution inverse of A218482.

Crossrefs

Programs

  • Maple
    a:=series(mul((1-x^k/(1-x)^k),k=1..100),x=0,35): seq(coeff(a,x,n),n=0..34); # Paolo P. Lava, Apr 02 2019
  • Mathematica
    nmax = 35; CoefficientList[Series[Product[(1 - x^k/(1 - x)^k), {k, 1, nmax}], {x, 0, nmax}], x]

A137151 Triangle read by rows: A007318 * A026794.

Original entry on oeis.org

1, 2, 1, 5, 2, 1, 13, 4, 3, 1, 34, 9, 6, 4, 1, 88, 22, 11, 10, 5, 1, 225, 55, 22, 20, 15, 6, 1, 569, 137, 50, 36, 35, 21, 7, 1, 1425, 338, 122, 65, 70, 56, 28, 8, 1, 3538, 826, 302, 130, 127, 126, 84, 36, 9, 1, 8717, 2002, 740, 296, 221, 252, 210, 120, 45, 10, 1
Offset: 1

Views

Author

Gary W. Adamson, Jan 23 2008

Keywords

Comments

Row sums = A103446: (1, 3, 8, 21, 54, 137, 344, ...).

Examples

			First few rows of the triangle:
    1;
    2,   1;
    5,   2,  1;
   13,   4,  3,  1;
   34,   9,  6,  4,  1;
   88,  22, 11, 10,  5,  1;
  225,  55, 22, 20, 15,  6, 1;
  569, 137, 50, 36, 35, 21, 7, 1;
  ...
		

Crossrefs

Formula

Binomial transform of the partition triangle, A026794.

A307679 Expansion of e.g.f. Product_{k>=1} 1/(1 - x^k/(1 - x)^k)^(1/k).

Original entry on oeis.org

1, 1, 5, 35, 323, 3679, 49819, 781465, 13923545, 277563617, 6118251461, 147715469131, 3875706370315, 109781717161375, 3338229675519803, 108443658227589329, 3747688533281296049, 137273241169036231105, 5311844045472206624005, 216505267421266611639667, 9270689769095765333645651
Offset: 0

Views

Author

Ilya Gutkovskiy, Apr 21 2019

Keywords

Examples

			E.g.f.: A(x) = 1 + x + 5*x^2/2! + 35*x^3/3! + 323*x^4/4! + 3679*x^5/5! + 49819*x^6/6! + 781465*x^7/7! + 13923545*x^8/8! + ...
log(A(x)) = x + 4*x^2/2 + 11*x^3/3 + 27*x^4/4 + 62*x^5/5 + 137*x^6/6 + 296*x^7/7 + 630*x^8/8 + 1326*x^9/9 + ... + A160399(k)*x^k/k + ...
		

Crossrefs

Programs

  • Mathematica
    nmax = 20; CoefficientList[Series[Product[1/(1 - x^k/(1 - x)^k)^(1/k), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
    nmax = 20; CoefficientList[Series[Exp[Sum[DivisorSigma[0, k] x^k/(k (1 - x)^k), {k, 1, nmax}]], {x, 0, nmax}], x] Range[0, nmax]!

Formula

E.g.f.: exp(Sum_{k>=1} d(k)*x^k/(k*(1 - x)^k)), where d(k) is the number of divisors of k (A000005).
a(n) = Sum_{k=0..n} binomial(n-1,k-1)*A028342(k)*n!/k!.
Showing 1-9 of 9 results.