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 1-6 of 6 results.

A195242 Expansion of Sum_{n>=0} n^n*x^n/(1 - n*x)^n.

Original entry on oeis.org

1, 1, 5, 44, 548, 8808, 173352, 4036288, 108507968, 3307368320, 112703108480, 4245680193024, 175200825481728, 7859411394860032, 380810598813553664, 19819617775693512704, 1102737068471914938368, 65316500202537025634304, 4103422475123595857854464
Offset: 0

Views

Author

Paul D. Hanna, Sep 13 2011

Keywords

Comments

Compare g.f. to the identity (cf. A001710):
Sum_{n>=0} n^n*x^n/(1 + n*x)^n = 1 + (1/2)*Sum_{n>=1} (n+1)!*x^n.

Examples

			G.f.: A(x) = 1 + x + 5*x^2 + 44*x^3 + 548*x^4 + 8808*x^5 + 173352*x^6 +...
where
A(x) = 1 + x/(1-x) + 2^2*x^2/(1-2*x)^2 + 3^3*x^3/(1-3*x)^3 + 4^4*x^4/(1-4*x)^4 +...
		

Crossrefs

Programs

  • Mathematica
    a[n_] := Sum[Binomial[n - 1, k] (k + 1)^n, {k, 0, n}];
    Table[a[n], {n, 0, 18}] (* Jean-François Alcover, Jun 26 2019 *)
  • PARI
    {a(n)=polcoeff(sum(m=0,n,m^m*x^m/(1-m*x+x*O(x^n))^m),n)}
    
  • PARI
    {a(n)=sum(k=0,n,binomial(n-1,k)*(k+1)^n)}
    
  • PARI
    {a(n)=(n+1)!/2 + 2*sum(k=0,n\2,binomial(n-1,n-2*k)*(n-2*k+1)^n)}

Formula

a(n) = Sum_{k=0..n} C(n-1,k)*(k+1)^n.
a(n) = (n+1)!/2 + 2*Sum_{k=0..[n/2]} C(n-1,n-2*k)*(n-2*k+1)^n for n>0 with a(0)=1.
a(n) ~ n^n * r^(n+3/2) / (exp(n) * (1-r)^n), where r = 1/(1+LambertW(exp(-1))) = 0.78218829428019990122... . - Vaclav Kotesovec, May 14 2014
a(n) = Sum_{k=0..n} (-1)^(n-k)*binomial(-k,-n)*k^n. Cf. A053506. - Peter Luschny, Apr 11 2016

A242446 a(n) = Sum_{k=1..n} C(n,k) * k^(2*n).

Original entry on oeis.org

1, 18, 924, 93320, 15609240, 3903974592, 1364509038592, 635177480713344, 379867490829555840, 283825251434680651520, 259092157573229145859584, 283735986144895532781391872, 367138254141051794797009309696, 554136240038549806366753446051840
Offset: 1

Views

Author

Vaclav Kotesovec, May 14 2014

Keywords

Comments

Generally, for p>=1, a(n) = Sum_{k=1..n} C(n,k) * k^(p*n) is asymptotic to sqrt(r/(p+r-p*r)) * r^(p*n) * n^(p*n) / (exp(p*n) * (1-r)^n), where r = p/(p+LambertW(p*exp(-p))).
Sum_{k=1..n} (-1)^(n-k) * C(n,k) * k^(p*n) = n! * stirling2(p*n,n).

Crossrefs

Programs

  • Mathematica
    Table[Sum[Binomial[n,k]*k^(2*n),{k,1,n}],{n,1,20}]

Formula

a(n) ~ sqrt(r/(2-r)) * r^(2*n) * n^(2*n) / (exp(2*n) * (1-r)^n), where r = 2/(2+LambertW(2*exp(-2))).

A220955 O.g.f.: Sum_{n>=0} (2*n+1)^(2*n+1) * exp(-(2*n+1)^2*x) * x^n / n!.

Original entry on oeis.org

1, 26, 1320, 99288, 9901920, 1230768704, 183260197120, 31800433551744, 6301891570411008, 1404224096732154880, 347532097449969496064, 94584986134590717358080, 28076463606243146379018240, 9027122730610037995425792000, 3125219575155651450096795648000
Offset: 0

Views

Author

Paul D. Hanna, Feb 27 2013

Keywords

Comments

From Vaclav Kotesovec, May 13 2014: (Start)
Generally, for p>1, a(n) = 1/n! * Sum_{k=0..n} (-1)^(n-k)*binomial(n,k) * (p*k+1)^(p*n+1) = Sum_{k=0..(p-1)*n+1} p^(n+k) * binomial(p*n+1,n+k) * stirling2(n+k,n).
a(n) ~ n^(n*p-n+1/2) * p^(2*p*n+2+1/p) / (sqrt(2*Pi*(1-r)) * exp((p-1)*n) * r^(n+1/p) * (p-r)^(n*p-n+1)), where r = -LambertW(-p*exp(-p)).
(End)

Examples

			O.g.f.: A(x) = 1 + 26*x + 1320*x^2 + 99288*x^3 + 9901920*x^4 +...
where A(x) = exp(-x) + 3^3*exp(-3^2*x)*x + 5^5*exp(-5^2*x)*x^2/2! + 7^7*exp(-7^2*x)*x^3/3! + 9^9*exp(-9^2*x)*x^4/4! + 11^11*exp(-11^2*x)*x^5/5! +...
is a power series in x with integer coefficients.
		

Crossrefs

Programs

  • Mathematica
    Table[1/n! * Sum[(-1)^(n-k)*Binomial[n,k] * (2*k+1)^(2*n+1),{k,0,n}],{n,0,20}] (* Vaclav Kotesovec, May 13 2014 *)
    Table[Sum[Binomial[2*n+1,n+k]*2^(n+k)*StirlingS2[n+k,n],{k,0,n+1}],{n,0,20}] (* Vaclav Kotesovec, May 13 2014 *)
  • PARI
    {a(n)=polcoeff(sum(k=0, n, (2*k+1)^(2*k+1)*exp(-(2*k+1)^2*x +x*O(x^n))*x^k/k!), n)}
    for(n=0, 20, print1(a(n), ", "))
    
  • PARI
    {a(n)=(1/n!)*polcoeff(sum(k=0, n, (2*k+1)^(2*k+1)*x^k/(1+(2*k+1)^2*x +x*O(x^n))^(k+1)), n)}
    for(n=0, 20, print1(a(n), ", "))
    
  • PARI
    {a(n)=1/n!*sum(k=0, n, (-1)^(n-k)*binomial(n, k)*(2*k+1)^(2*n+1))}
    for(n=0, 20, print1(a(n), ", "))

Formula

a(n) = 1/n! * [x^n] Sum_{k>=0} (2*k+1)^(2*k+1) * x^k / (1 + (2*k+1)^2*x)^(k+1).
a(n) = 1/n! * Sum_{k=0..n} (-1)^(n-k)*binomial(n,k) * (2*k+1)^(2*n+1).
a(n) = Sum_{k=0..n+1} 2^(n+k) * binomial(2*n+1,n+k) * stirling2(n+k,n). - Vaclav Kotesovec, May 13 2014
a(n) ~ n^(n+1/2) * 2^(4*n+5/2) / (sqrt(2*Pi*(1-r)) * exp(n) * r^(n+1/2) * (2-r)^(n+1)), where r = -LambertW(-2*exp(-2)) = 0.4063757399599599... (see A226775 = -r) . - Vaclav Kotesovec, May 13 2014

A221214 O.g.f.: Sum_{n>=0} (3*n+1)^(3*n+1) * exp(-(3*n+1)^3*x) * x^n / n!.

Original entry on oeis.org

1, 255, 395388, 1525953330, 10977340509135, 126827739333023274, 2148335345336441463090, 50163717301669569182864400, 1544377393328765493716910877185, 60615459491155396034172113103266025, 2954227738557038665136475801709196246304
Offset: 0

Views

Author

Paul D. Hanna, Feb 27 2013

Keywords

Examples

			O.g.f.: A(x) = 1 + 255*x + 395388*x^2 + 1525953330*x^3 + 10977340509135*x^4 +...
where A(x) = exp(-x) + 4^4*x*exp(-4^3*x) + 7^7*exp(-7^3*x)*x^2/2! + 10^10*exp(-10^3*x)*x^3/3! + 13^13*exp(-13^3*x)*x^4/4! + 16^16*exp(-16^3*x)*x^5/5! +... is a power series in x with integer coefficients.
		

Crossrefs

Programs

  • Mathematica
    Table[1/n!*Sum[(-1)^(n-k)*Binomial[n,k]*(3*k+1)^(3*n+1),{k,0,n}],{n,0,20}] (* Vaclav Kotesovec, May 13 2014 *)
    Table[Sum[Binomial[3*n+1,n+k]*3^(n+k)*StirlingS2[n+k,n],{k,0,2*n+1}],{n,0,20}] (* Vaclav Kotesovec, May 13 2014 *)
  • PARI
    {a(n)=polcoeff(sum(k=0, n, (3*k+1)^(3*k+1)*exp(-(3*k+1)^3*x +x*O(x^n))*x^k/k!), n)}
    for(n=0, 20, print1(a(n), ", "))
    
  • PARI
    {a(n)=(1/n!)*polcoeff(sum(k=0, n, (3*k+1)^(3*k+1)*x^k/(1+(3*k+1)^3*x +x*O(x^n))^(k+1)), n)}
    for(n=0, 20, print1(a(n), ", "))
    
  • PARI
    {a(n)=1/n!*sum(k=0, n, (-1)^(n-k)*binomial(n, k)*(3*k+1)^(3*n+1))}
    for(n=0, 20, print1(a(n), ", "))

Formula

a(n) = 1/n! * [x^n] Sum_{k>=0} (3*k+1)^(3*k+1) * x^k / (1 + (3*k+1)^3*x)^(k+1).
a(n) = 1/n! * Sum_{k=0..n} (-1)^(n-k)*binomial(n,k) * (3*k+1)^(3*n+1).
a(n) ~ n^(2*n+1/2) * 3^(6*n+7/3) / (sqrt(2*Pi*(1-r)) * exp(2*n) * r^(n+1/3) * (3-r)^(2*n+1)), where r = -LambertW(-3*exp(-3)) = 0.1785606278779211... (see A226750 = -r) . - Vaclav Kotesovec, May 13 2014

A213193 O.g.f.: Sum_{n>=0} (4*n+1)^(4*n+1) * exp(-(4*n+1)^4*x) * x^n / n!.

Original entry on oeis.org

1, 3124, 191757120, 49208861869440, 33030777426968816640, 45829974166034718596428800, 114009204539207742166715857223680, 462192193445890293982679086838571270144, 2851153321165202191241172917762717987236478976
Offset: 0

Views

Author

Paul D. Hanna, Mar 01 2013

Keywords

Comments

From Vaclav Kotesovec, May 13 2014: (Start)
Generally, for p>1, a(n) = 1/n! * Sum_{k=0..n} (-1)^(n-k)*binomial(n,k) * (p*k+1)^(p*n+1) = Sum_{k=0..(p-1)*n+1} p^(n+k) * binomial(p*n+1,n+k) * stirling2(n+k,n).
a(n) ~ n^(n*p-n+1/2) * p^(2*p*n+2+1/p) / (sqrt(2*Pi*(1-r)) * exp((p-1)*n) * r^(n+1/p) * (p-r)^(n*p-n+1)), where r = -LambertW(-p*exp(-p)).
(End)

Examples

			O.g.f.: A(x) = 1 + 3124*x + 191757120*x^2 + 49208861869440*x^3 +...
where
A(x) = exp(-x) + 5^5*x*exp(-5^4*x) + 9^9*exp(-9^4*x)*x^2/2! + 13^13*exp(-13^4*x)*x^3/3! + 17^17*exp(-17^4*x)*x^4/4! + 21^21*exp(-21^4*x)*x^5/5! +...
is a power series in x with integer coefficients.
		

Crossrefs

Programs

  • Mathematica
    Table[1/n!*Sum[(-1)^(n-k)*Binomial[n,k]*(4*k+1)^(4*n+1),{k,0,n}],{n,0,20}] (* Vaclav Kotesovec, May 13 2014 *)
    Table[Sum[Binomial[4*n+1,n+k]*4^(n+k)*StirlingS2[n+k,n],{k,0,3*n+1}],{n,0,20}] (* Vaclav Kotesovec, May 13 2014 *)
  • PARI
    {a(n)=polcoeff(sum(k=0, n, (4*k+1)^(4*k+1)*exp(-(4*k+1)^4*x +x*O(x^n))*x^k/k!), n)}
    for(n=0, 20, print1(a(n), ", "))
    
  • PARI
    {a(n)=(1/n!)*polcoeff(sum(k=0, n, (4*k+1)^(4*k+1)*x^k/(1+(4*k+1)^4*x +x*O(x^n))^(k+1)), n)}
    for(n=0, 20, print1(a(n), ", "))
    
  • PARI
    {a(n)=1/n!*sum(k=0, n, (-1)^(n-k)*binomial(n, k)*(4*k+1)^(4*n+1))}
    for(n=0, 20, print1(a(n), ", "))

Formula

a(n) = 1/n! * [x^n] Sum_{k>=0} (4*k+1)^(4*k+1) * x^k / (1 + (4*k+1)^4*x)^(k+1).
a(n) = 1/n! * Sum_{k=0..n} (-1)^(n-k)*binomial(n,k) * (4*k+1)^(4*n+1).
a(n) ~ n^(3*n+1/2) * 2^(16*n+9/2) / (sqrt(2*Pi*(1-r)) * exp(3*n) * r^(n+1/4) * (4-r)^(3*n+1)), where r = -LambertW(-4*exp(-4)) = 0.0793096051271136564391... . - Vaclav Kotesovec, May 13 2014

A242373 Sum_{k=0..n} C(n,k) * (2*k+1)^(2*n).

Original entry on oeis.org

1, 10, 788, 166712, 68475920, 46294050592, 46645589472064, 65553860981315968, 122544885380995907840, 294065070661381857417728, 881074796163065604590326784, 3223847668121045228481269463040, 14146460882056535042193752974692352
Offset: 0

Views

Author

Vaclav Kotesovec, May 12 2014

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Sum[Binomial[n,k]*(2*k+1)^(2*n),{k,0,n}],{n,0,20}]

Formula

a(n) ~ 2^(2*n) * n^(2*n) * r^(2*n+1) / (sqrt(2-r) * exp(2*n) * (1-r)^(n+1/2)), where r = 2/(2+LambertW(2*exp(-2))) = 0.901829091937052... . - Vaclav Kotesovec, May 14 2014
Showing 1-6 of 6 results.