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 1-2 of 2 results.

A385425 Expansion of e.g.f. exp( -LambertW(-arcsinh(x)) ).

Original entry on oeis.org

1, 1, 3, 15, 113, 1145, 14499, 220703, 3932865, 80342577, 1851286755, 47510525007, 1344106404849, 41562628517865, 1394711974335939, 50480840239135455, 1960392617938419969, 81309789407316485217, 3587373056789171999811, 167762667997938465311247
Offset: 0

Views

Author

Seiichi Manyama, Jun 28 2025

Keywords

Crossrefs

Programs

  • PARI
    my(N=20, x='x+O('x^N)); Vec(serlaplace(exp(-lambertw(-asinh(x)))))

Formula

E.g.f. A(x) satisfies A(x) = exp( arcsinh(x) * A(x) ).
E.g.f. A(x) satisfies A(x) = ( x + sqrt(x^2 + 1) )^A(x).
a(n) = Sum_{k=0..n} (k+1)^(k-1) * i^(n-k) * A385343(n,k), where i is the imaginary unit.
From Vaclav Kotesovec, Jun 28 2025: (Start)
a(n) ~ 2^n * exp((exp(-1) - 1)*n + 3/2) * n^(n-1) / (sqrt(1 + exp(2*exp(-1))) * (exp(2*exp(-1)) - 1)^(n - 1/2)).
Equivalently, a(n) ~ n^(n-1) / (sqrt(cosh(exp(-1))) * sinh(exp(-1))^(n - 1/2) * exp(n - 3/2)). (End)

A385502 E.g.f. A(x) satisfies A(x) = exp( arctanh(x * A(x)) / A(x) ).

Original entry on oeis.org

1, 1, 1, 3, 25, 205, 2001, 25991, 394353, 6718041, 130319745, 2833146987, 67767170505, 1772434086501, 50392083769041, 1546052750636655, 50905035315373281, 1790951445870568113, 67050161599822764417, 2661363261252799648083, 111637709182606749500025
Offset: 0

Views

Author

Seiichi Manyama, Jul 01 2025

Keywords

Crossrefs

Programs

  • Mathematica
    terms = 21; A[] = 1; Do[A[x] = Exp[ArcTanh[x*A[x]]/A[x]] + O[x]^terms // Normal, terms]; CoefficientList[A[x], x]Range[0,terms-1]! (* Stefano Spezia, Jul 01 2025 *)
  • PARI
    a111594(n, k) = my(x='x+O('x^(n+1))); n!*polcoef(atanh(x)^k/k!, n);
    a(n) = sum(k=0, n, (n-k+1)^(k-1)*a111594(n, k));

Formula

E.g.f. A(x) satisfies A(x) = ( (1+x*A(x))/(1-x*A(x)) )^(1/(2*A(x))).
a(n) = Sum_{k=0..n} (n-k+1)^(k-1) * A111594(n,k).
a(n) ~ s * sqrt((-1 + r^2*s^2)/(1 - 2*r^2*(1 + r)*s^2 + r^4*s^4)) * n^(n-1) / (exp(n) * r^(n - 1/2)), where r = 0.4422573061236400123439455590007131605377062990202... and s = 1.93686591146053883124948614770176661449449740697... are the roots of the system of equations ((1 + r*s)/(1 - r*s))^(1/2/s) = s, 2*r*s + (-1 + r^2*s^2)*(log((1 + r*s)/(1 - r*s)) + 2*s) = 0. - Vaclav Kotesovec, Jul 01 2025
Showing 1-2 of 2 results.