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.

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A277682 Decimal expansion of the imaginary part of the fixed point of exp(z) in C congruent with the branch K=1 of log(z)+2*Pi*K*i.

Original entry on oeis.org

7, 5, 8, 8, 6, 3, 1, 1, 7, 8, 4, 7, 2, 5, 1, 2, 6, 2, 2, 5, 6, 8, 9, 2, 3, 9, 5, 4, 1, 0, 7, 5, 8, 4, 3, 8, 3, 0, 1, 3, 4, 7, 3, 6, 7, 1, 9, 9, 2, 8, 5, 6, 3, 6, 0, 4, 0, 9, 4, 3, 7, 4, 3, 7, 3, 6, 4, 3, 2, 2, 7, 5, 6, 0, 2, 3, 4, 0, 4, 8, 7, 2, 5, 0, 4, 7, 3, 3, 2, 7, 1, 5, 4, 7, 0, 5, 0, 1, 9, 3, 0, 5, 0, 7, 3
Offset: 1

Views

Author

Stanislav Sykora, Nov 12 2016

Keywords

Comments

Imaginary part of the complex constant z_3 whose real part is in A277681 (see the latter entry for more information).

Examples

			7.588631178472512622568923954107584383013473671992856360409437...
		

Crossrefs

Fixed points of +exp(z): z_1: A059526, A059527, A238274, and z_3: A277681 (real part), A277683 (modulus).
Fixed points of -exp(z): z_0: A030178, and z_2: A276759, A276760, A276761.

Programs

  • Mathematica
    RealDigits[Im[ProductLog[1, -1]], 10, 105][[1]] (* Jean-François Alcover, Nov 12 2016 *)
  • PARI
    default(realprecision,2050);eps=5.0*10^(default(realprecision))
    M(z,K)=log(z)+2*Pi*K*I; \\ the convergent mapping (any K)
    K=1;z=1+I;zlast=z;
    while(1,z=M(z,K);if(abs(z-zlast)
    				

Formula

Let z_3 = A277681+i*A277682. Then z_3 = exp(z_3) = log(z_3)+2*Pi*i = -W_-2(-1).

A277683 Decimal expansion of the modulus of the fixed point of exp(z) in C congruent with the branch K=1 of log(z)+2*Pi*K*i.

Original entry on oeis.org

7, 8, 6, 3, 8, 6, 1, 1, 7, 6, 0, 9, 4, 2, 3, 2, 6, 6, 8, 8, 4, 2, 5, 7, 3, 6, 2, 3, 4, 8, 7, 3, 8, 2, 3, 2, 1, 4, 6, 8, 3, 2, 0, 2, 0, 7, 7, 7, 9, 8, 9, 3, 4, 6, 0, 2, 9, 4, 1, 4, 4, 5, 3, 0, 5, 7, 4, 5, 8, 5, 9, 2, 4, 3, 3, 2, 5, 2, 0, 4, 5, 8, 8, 8, 0, 1, 1, 0, 4, 5, 8, 7, 4, 9, 0, 6, 6, 4, 4, 6, 4, 0, 3, 8, 1
Offset: 1

Views

Author

Stanislav Sykora, Nov 12 2016

Keywords

Comments

Modulus of z_3 = A277681 + i*A277682. See A277681 for more information.

Examples

			7.863861176094232668842573623487382321468320207779893460294144...
		

Crossrefs

Fixed points of +exp(z): z_1: A059526, A059527, A238274, and z_3: A277681 (real part), A277682 (imaginary part).
Fixed points of -exp(z): z_0: A030178, and z_2: A276759, A276760, A276761.

Programs

  • Mathematica
    RealDigits[Norm[ProductLog[1, -1]], 10, 105][[1]] (* Jean-François Alcover, Nov 12 2016 *)
  • PARI
    default(realprecision,2050);eps=5.0*10^(default(realprecision))
    M(z,K)=log(z)+2*Pi*K*I; \\ the convergent mapping (any K)
    K=1;z=1+I;zlast=z;
    while(1,z=M(z,K);if(abs(z-zlast)
    				

A126583 Decimal expansion of solution to exp(-x) = x^2.

Original entry on oeis.org

7, 0, 3, 4, 6, 7, 4, 2, 2, 4, 9, 8, 3, 9, 1, 6, 5, 2, 0, 4, 9, 8, 1, 8, 6, 0, 1, 8, 5, 9, 9, 0, 2, 1, 3, 0, 3, 4, 2, 9, 2, 8, 4, 3, 1, 0, 3, 4, 2, 2, 3, 6, 0, 8, 0, 9, 3, 2, 8, 7, 6, 9, 2, 2, 1, 9, 9, 2, 1, 2, 2, 1, 4, 4, 0, 6, 7, 7, 4, 2, 1, 7, 9, 3, 6, 6, 4, 6, 0, 7, 6, 6, 4, 3, 8, 3, 1, 3, 8, 5, 4, 7
Offset: 0

Views

Author

Denton J. Dailey (djd1497(AT)aol.com), Jan 05 2007

Keywords

Comments

The value of the infinite power tower function x^x^x... at x = sqrt(1/e). - Alois P. Heinz, Oct 19 2016

Examples

			0.7034674224983916520498186018599021303429284310342236...
		

Crossrefs

Programs

  • Mathematica
    RealDigits[ FindRoot[ Exp[ -x] == x^2, {x, {.5, 1}}, WorkingPrecision -> 120][[1, 2, 1]], 10, 111][[1]]
    RealDigits[ 2*ProductLog[1/2], 10, 102] // First (* Jean-François Alcover, Feb 27 2013 *)
  • PARI
    2*lambertw(1/2) \\ G. C. Greubel, Mar 06 2018

Formula

Equals 2*LambertW(1/2). - Alois P. Heinz, Oct 19 2016
Equals log(A099554) = 2*A202356. - Hugo Pfoertner, Jul 19 2024

A198860 E.g.f. satisfies A(x) = 1/(1 - log(1 + x*A(x))).

Original entry on oeis.org

1, 1, 3, 17, 144, 1634, 23312, 401274, 8096680, 187472136, 4900535832, 142766286552, 4587190461840, 161161214978880, 6146415080939520, 252902928346825104, 11167368115492742400, 526752556713346955520, 26433830208985721222400, 1406218428780691953635712
Offset: 0

Views

Author

Paul D. Hanna, Oct 30 2011

Keywords

Comments

Compare to e.g.f. G(x) of A052802, which satisfies: G(x) = 1/(1 + log(1 - x*G(x))).

Examples

			E.g.f.: A(x) = 1 + x + 3*x^2/2! + 17*x^3/3! + 144*x^4/4! + 1634*x^5/5! + ...
where log(1 + x*A(x)) equals
1 - 1/A(x) = x + x^2/2! + 5*x^3/3! + 38*x^4/4! + 404*x^5/5! + 5514*x^6/6! + ...
		

Crossrefs

Programs

  • Mathematica
    a[n_] := Sum[ Binomial[n+k, n]*Sum[ (-1)^(j)*Binomial[k, j]*Sum[ (-1)^i*i!*Binomial[j, i]*StirlingS1[n, i], {i, 0, j}], {j, 0, k}], {k, 0, n}]/(n+1); Table[a[n], {n, 0, 19}] (* Jean-François Alcover, Jun 24 2013, after Vladimir Kruchinin *)
    CoefficientList[1/x*InverseSeries[Series[x-x*Log[1+x], {x, 0, 20}], x],x] * Range[0, 19]! (* Vaclav Kotesovec, Dec 28 2013 *)
  • Maxima
    a(n):=sum(binomial(n+k,n)*sum((-1)^(j)*binomial(k,j)*sum((-1)^i*i!*binomial(j,i)* stirling1(n,i),i,0,j),j,0,k),k,0,n)/(n+1); /* Vladimir Kruchinin, Feb 04 2012 */
  • PARI
    {a(n)=n!*polcoeff((1/x)*serreverse(x-x*log(1+x +x*O(x^n))),n)}
    
  • PARI
    {a(n)=n!*polcoeff(1/(1-log(1+x +x*O(x^n)))^(n+1)/(n+1),n)}
    
  • PARI
    /* by Vladimir Kruchinin's formula: */
    {a(n)=sum(k=0,n,binomial(n+k,n)*sum(j=0,k,(-1)^(j)*binomial(k,j)*sum(i=0,j,(-1)^i*i!*binomial(j,i)*stirling(n,i,1))))/(n+1)}
    

Formula

E.g.f. satisfies: A(x*(1 - log(1+x))) = 1/(1 - log(1+x)).
E.g.f.: A(x) = (1/x)*Series_Reversion[x - x*log(1+x)].
a(n) = n!*[x^n] 1/(1 - log(1+x))^(n+1)/(n+1).
a(n) = Sum_{k=0..n} (binomial(n+k,n) * Sum_{j=0..k} (-1)^(j)*binomial(k,j) * (Sum_{i=0..j} (-1)^i*i!*binomial(j,i)*Stirling1(n,i)))/(n+1). - Vladimir Kruchinin, Feb 04 2012
a(n) ~ n^(n-1) / ((1-c)*sqrt(1+c) * exp(n) * (1/c+c-2)^n), where c = LambertW(1). - Vaclav Kotesovec, Dec 28 2013
a(n) = (1/(n+1)!) * Sum_{k=0..n} (n+k)! * Stirling1(n,k). - Seiichi Manyama, Nov 06 2023

A245265 E.g.f. satisfies: A(x) = exp(x/(1-x*A(x)^4)).

Original entry on oeis.org

1, 1, 3, 37, 649, 15461, 471571, 17456041, 760880625, 38178439849, 2167446089251, 137359883836781, 9612722107574521, 736277501363180557, 61265207586681046131, 5503291392884323494961, 530778414439201798454881, 54706967800114521799571921, 6000952913613549583603208515
Offset: 0

Views

Author

Vaclav Kotesovec, Jul 15 2014

Keywords

Comments

Generally, if e.g.f. satisfies: A(x) = exp(x/(1-x*A(x)^p)), p>=1, then
r = 4*LambertW(sqrt(p)/2)^2 / (p*(1+2*LambertW(sqrt(p)/2))),
A(r) = (sqrt(p)/(2*LambertW(sqrt(p)/2)))^(2/p),
a(n) ~ p^(n-1+1/p) * (1+2*LambertW(sqrt(p)/2))^(n+1/2) * n^(n-1) / (sqrt(1+LambertW(sqrt(p)/2)) * exp(n) * 2^(2*n+2/p) * LambertW(sqrt(p)/2)^(2*n+2/p-1/2)).

Examples

			E.g.f.: A(x) = 1 + x + 3*x^2/2! + 37*x^3/3! + 649*x^4/4! + 15461*x^5/5! + 471571*x^6/6! + ...
		

Crossrefs

Cf. A161630 (p=1), A212722 (p=2), A212917 (p=3).
Cf. A030178.
Cf. A366234 (log).

Programs

  • Mathematica
    Table[Sum[n! * (1 + 4*(n-k))^(k-1)/k! * Binomial[n-1,n-k],{k,0,n}],{n,0,20}]
  • PARI
    for(n=0,30, print1(sum(k=0,n, n!*(1 + 4*(n-k))^(k-1)/k!*binomial(n-1,n-k)), ", ")) \\ G. C. Greubel, Nov 17 2017

Formula

a(n) = Sum_{k=0..n} n! * (1 + 4*(n-k))^(k-1)/k! * C(n-1,n-k).
a(n) ~ n^(n-1) * (1+2*LambertW(1))^(n+1/2) / (exp(n) * (LambertW(1))^(2*n) * (4*sqrt(1+LambertW(1)))). - Vaclav Kotesovec, Jul 15 2014

A369090 Expansion of e.g.f. A(x) satisfying A(x) = A( x^2*exp(x) ) / x, with A(0) = 0.

Original entry on oeis.org

1, 2, 9, 52, 425, 4206, 48307, 632360, 9444465, 159240250, 2983729331, 61300668012, 1367054727337, 32844312889766, 845234187028155, 23190947446000336, 675895337644401377, 20863665943202969586, 680448552777544884643, 23395823324931227353940, 846248620848062865320601
Offset: 1

Views

Author

Paul D. Hanna, Jan 26 2024

Keywords

Comments

Limit (a(n)/n!)^(1/n) = 1/w where w*exp(w) = 1 and w = LambertW(1) = 0.567143290409783872999968... (cf. A030178).

Examples

			E.g.f.: A(x) = x + 2*x^2/2! + 9*x^3/3! + 52*x^4/4! + 425*x^5/5! + 4206*x^6/6! + 48307*x^7/7! + 632360*x^8/8! + 9444465*x^9/9! + 159240250*x^10/10! + ...
RELATED SERIES.
The expansion of the logarithm of A(x)/x starts
log(A(x)/x) = x + 2*x^2/2! + 6*x^3/3! + 36*x^4/4! + 260*x^5/5! + 2190*x^6/6! + 21882*x^7/7! + 268856*x^8/8! + ... + A369091(n)*x^n/n! + ...
and equals the sum of all iterations of the function x^2*exp(x).
Let R(x) be the series reversion of A(x),
R(x) = x - 2*x^2/2! + 3*x^3/3! + 8*x^4/4! - 155*x^5/5! + 1464*x^6/6! - 7931*x^7/7! - 65360*x^8/8! + 2742345*x^9/9! + ...
then R(x) and e.g.f. A(x) satisfy:
(1) R( A(x) ) = x,
(2) R( x*A(x) ) = x^2 * exp(x).
GENERATING METHOD.
Let F(n) equal the n-th iteration of x^2*exp(x), so that
F(0) = x,
F(1) = x^2 * exp(x),
F(2) = x^4 * exp(2*x) * exp(x^2*exp(x)),
F(3) = x^8 * exp(4*x) * exp(2*x^2*exp(x)) * exp(F(2)),
F(4) = x^16 * exp(8*x) * exp(4*x^2*exp(x)) * exp(2*F(2)) * exp(F(3)),
F(5) = x^32 * exp(16*x) * exp(8*x^2*exp(x)) * exp(4*F(2)) * exp(2*F(3)) * exp(F(4)),
...
F(n+1) = F(n)^2 * exp(F(n))
...
Then the e.g.f. A(x) equals
A(x) = x * exp(F(0) + F(1) + F(2) + F(3) + ... + F(n) + ...).
equivalently,
A(x) = x * exp(x + x^2*exp(x) + x^4*exp(2*x)*exp(x^2*exp(x)) + x^8*exp(4*x)*exp(2*x^2*exp(x)) * exp(x^4*exp(2*x)*exp(x^2*exp(x))) + ...).
		

Crossrefs

Cf. A369091, A369550 (a(n)/n), A030178.
Cf. A367390.

Programs

  • PARI
    {a(n) = my(A=x); for(i=0, #binary(n),
    A = subst(A, x, x^2*exp(x +x^2*O(x^n)) )/x ); n! * polcoeff(H=A, n)}
    for(n=1, 30, print1(a(n), ", "))

Formula

E.g.f. A(x) = Sum_{n>=1} a(n)*x^n/n! satisfies the following formulas.
(1) A(x) = A(x^2*exp(x)) / x.
(2) R(x*A(x)) = x^2*exp(x), where R(A(x)) = x.
(3) A(x) = x * exp( Sum_{n>=0} F(n) ), where F(0) = x, and F(n+1) = F(n)^2 * exp(F(n)) for n >= 0.
(4) A(x) = x * exp(L(x)), where L(x) = x + L(x^2*exp(x)) is the e.g.f. of A369091.

A299617 Decimal expansion of e^(W(1) + W(e)) = e/(W(1)*W(e)), where W is the Lambert W function (or PowerLog); see Comments.

Original entry on oeis.org

4, 7, 9, 2, 9, 3, 6, 5, 9, 0, 1, 4, 2, 8, 1, 4, 0, 2, 5, 7, 2, 5, 8, 4, 7, 3, 7, 2, 3, 8, 2, 1, 0, 8, 6, 0, 1, 5, 9, 6, 7, 8, 6, 3, 9, 6, 2, 8, 4, 3, 7, 6, 3, 9, 1, 3, 6, 6, 9, 9, 8, 4, 6, 8, 1, 6, 8, 5, 7, 7, 9, 5, 1, 4, 5, 2, 0, 4, 4, 0, 1, 7, 7, 4, 8, 4
Offset: 1

Views

Author

Clark Kimberling, Mar 01 2018

Keywords

Comments

The Lambert W function satisfies the functional equation e^(W(x) + W(y)) = x*y/(W(x)*W(y)) for x and y greater than -1/e, so that e^(W(1) + W(e)) = e/(W(1)*W(e)). See A299613 for a guide to related constants.

Examples

			e^(W(1) + W(e)) = 4.7929365901428140257258473723821086015...
		

Crossrefs

Programs

  • Mathematica
    w[x_] := ProductLog[x]; x = 1; y = E;
    N[E^(w[x] + w[y]), 130]   (* A299617 *)
    RealDigits[E/(LambertW[1]*LambertW[E]), 10, 100][[1]] (* G. C. Greubel, Mar 03 2018 *)
  • PARI
    exp(1)/(lambertw(1)*lambertw(exp(1))) \\ G. C. Greubel, Mar 03 2018

A300916 Decimal expansion of the first derivative of the infinite power tower function x^x^x... at x = 1/e.

Original entry on oeis.org

5, 5, 7, 9, 1, 9, 2, 8, 2, 2, 5, 5, 4, 1, 6, 0, 4, 6, 7, 7, 3, 8, 6, 4, 7, 3, 3, 1, 3, 7, 2, 8, 4, 3, 2, 5, 2, 6, 8, 0, 5, 9, 5, 2, 2, 1, 4, 7, 0, 0, 0, 5, 6, 8, 8, 5, 6, 8, 6, 1, 6, 7, 8, 6, 6, 5, 6, 6, 9, 1, 6, 8, 0, 8, 0, 0, 6, 2, 9, 0, 4, 7, 4, 3, 6, 9, 7, 5, 4, 6, 6, 9, 3, 4, 2, 8, 0, 5, 7, 8, 8, 8, 4, 1, 8, 2
Offset: 0

Views

Author

Alois P. Heinz, Mar 16 2018

Keywords

Examples

			0.557919282255416046773864733137284325268059522147000568856861678665669168...
		

Crossrefs

Programs

  • Mathematica
    RealDigits[E*Exp[-2*LambertW[1]]/(1+LambertW[1]), 10, 100][[1]] (* G. C. Greubel, Sep 09 2018 *)
  • PARI
    exp(1)*exp(-2*lambertw(1))/(1+lambertw(1)) \\ Michel Marcus, Mar 16 2018

Formula

Equals exp(1)*exp(-2*LambertW(1))/(1+LambertW(1)).

A369091 Expansion of e.g.f. A(x) satisfying A(x) = x + A( x^2*exp(x) ), with A(0) = 0.

Original entry on oeis.org

1, 2, 6, 36, 260, 2190, 21882, 268856, 3907080, 63977850, 1152946190, 22581979332, 477140664156, 10828556474918, 263163922847490, 6836792356168560, 189694001088036752, 5614994984290505586, 176964200467784915094, 5921022573291003915260, 209568707084236321665060
Offset: 1

Views

Author

Paul D. Hanna, Jan 26 2024

Keywords

Comments

Limit (a(n)/n!)^(1/n) = 1/w where w*exp(w) = 1 and w = LambertW(1) = 0.567143290409783872999968... (cf. A030178).

Examples

			E.g.f.: A(x) = x + 2*x^2/2! + 6*x^3/3! + 36*x^4/4! + 260*x^5/5! + 2190*x^6/6! + 21882*x^7/7! + 268856*x^8/8! + 3907080*x^9/9! + 63977850*x^10/10! + ...
which equals the sum of all iterations of the function x^2*exp(x).
RELATED SERIES.
x*exp(A(x)) = x + 2*x^2/2! + 9*x^3/3! + 52*x^4/4! + 425*x^5/5! + 4206*x^6/6! + 48307*x^7/7! + 632360*x^8/8! + ... + A369090(n)*x^n/n! + ...
Let R(x) be the series reversion of A(x),
R(x) = x - 2*x^2/2! + 6*x^3/3! - 36*x^4/4! + 340*x^5/5! - 3870*x^6/6! + 52038*x^7/7! - 850472*x^8/8! + 16378920*x^9/9! + ...
then R(x) and e.g.f. A(x) satisfy:
(1) R( A(x) ) = x,
(2) R( A(x) - x ) = x^2 * exp(x).
GENERATING METHOD.
Let F(n) equal the n-th iteration of x^2*exp(x), so that
F(0) = x,
F(1) = x^2 * exp(x),
F(2) = x^4 * exp(2*x) * exp(x^2*exp(x)),
F(3) = x^8 * exp(4*x) * exp(2*x^2*exp(x)) * exp(F(2)),
F(4) = x^16 * exp(8*x) * exp(4*x^2*exp(x)) * exp(2*F(2)) * exp(F(3)),
F(5) = x^32 * exp(16*x) * exp(8*x^2*exp(x)) * exp(4*F(2)) * exp(2*F(3)) * exp(F(4)),
...
F(n+1) = F(n)^2 * exp(F(n))
...
Then the e.g.f. A(x) equals the sum
A(x) = F(0) + F(1) + F(2) + F(3) + ... + F(n) + ...
equivalently,
A(x) = x + x^2*exp(x) + x^4*exp(2*x)*exp(x^2*exp(x)) + x^8*exp(4*x)*exp(2*x^2*exp(x)) * exp(x^4*exp(2*x)*exp(x^2*exp(x))) + ...
		

Crossrefs

Cf. A369090, A369551 (a(n)/n), A030178.

Programs

  • PARI
    {a(n) = my(A=x); for(i=0, #binary(n),
    A = x + subst(A, x, x^2*exp(x +x^2*O(x^n)) )); n! * polcoeff(A, n)}
    for(n=1, 30, print1(a(n), ", "))

Formula

E.g.f. A(x) = Sum_{n>=1} a(n)*x^n/n! satisfies the following formulas.
(1) A(x) = x + A( x^2*exp(x) ).
(2) A(x) = Sum_{n>=0} F(n), where F(0) = x, and F(n+1) = F(n)^2 * exp(F(n)) for n >= 0.
(3) A(x) = log(G(x)/x) where G(x) = G(x^2*exp(x))/x is the e.g.f. of A369090.

A073231 Decimal expansion of (1/e)^(1/e)^(1/e).

Original entry on oeis.org

5, 0, 0, 4, 7, 3, 5, 0, 0, 5, 6, 3, 6, 3, 6, 8, 4, 0, 5, 4, 5, 1, 3, 4, 9, 0, 1, 3, 3, 7, 9, 0, 4, 5, 7, 2, 8, 0, 3, 4, 5, 3, 2, 1, 5, 3, 4, 2, 2, 8, 3, 0, 0, 6, 4, 9, 7, 9, 0, 9, 3, 5, 2, 7, 8, 3, 7, 5, 7, 3, 2, 1, 1, 6, 2, 6, 1, 4, 3, 3, 4, 4, 3, 5, 1, 0, 6, 5, 0, 8, 2, 6, 5, 0, 9, 6, 5, 7, 5, 8, 9, 9, 3, 4
Offset: 0

Views

Author

Rick L. Shepherd, Jul 22 2002

Keywords

Examples

			0.50047350056363684054513490133...
		

Crossrefs

Cf. A001113 (e), A068985 (1/e), A072364 ((1/e)^(1/e)), A030178 (limit of (1/e)^(1/e)^...^(1/e)), A073232 (((1/e)^(1/e))^(1/e)), A073227 (e^e^e).

Programs

  • Mathematica
    With[{c=1/E},RealDigits[c^c^c,10,120][[1]]] (* Harvey P. Dale, Jul 16 2025 *)
  • PARI
    exp(-1)^exp(-1)^exp(-1)
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