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 1-3 of 3 results.

A380042 E.g.f. A(x) satisfies A(x) = 1/sqrt( 1 - 2*x*exp(x*A(x)^2) ).

Original entry on oeis.org

1, 1, 5, 48, 697, 13640, 336771, 10053778, 352334753, 14183529480, 645073504435, 32715111226886, 1830671281889649, 112049330303532388, 7446824171300128811, 534068807341887943770, 41111698162393482004801, 3381089519620006418116976, 295869084136630532211207843
Offset: 0

Views

Author

Seiichi Manyama, Jan 10 2025

Keywords

Crossrefs

Programs

  • PARI
    my(N=20, x='x+O('x^N)); Vec(serlaplace(sqrt(serreverse(x/(1+2*x*exp(x)))/x)))
    
  • PARI
    a(n) = n!*sum(k=0, n, 2^k*k^(n-k)*binomial(n+1/2, k)/(n-k)!)/(2*n+1);

Formula

E.g.f.: sqrt( (1/x) * Series_Reversion(x/(1 + 2*x*exp(x))) ).
a(n) = (n!/(2*n+1)) * Sum_{k=0..n} 2^k * k^(n-k) * binomial(n+1/2,k)/(n-k)!.

A380093 E.g.f. A(x) satisfies A(x) = sqrt( 1 + 2*x*exp(x*A(x)) ).

Original entry on oeis.org

1, 1, 1, 6, 13, 180, 501, 13720, 34777, 2014992, 2512585, 491642976, -564313947, 181714012480, -836832558275, 95473740036480, -856984734161999, 68029327826567424, -954950936641491951, 63368301861354866176, -1238053892876418633155, 74904417332353810338816
Offset: 0

Views

Author

Seiichi Manyama, Jan 12 2025

Keywords

Crossrefs

Programs

  • PARI
    a(n) = n!*sum(k=0, n, 2^k*k^(n-k)*binomial(n/2-k/2+1/2, k)/((n-k+1)*(n-k)!));

Formula

a(n) = n! * Sum_{k=0..n} 2^k * k^(n-k) * binomial(n/2-k/2+1/2,k)/( (n-k+1)*(n-k)! ).

A380077 Expansion of e.g.f. (1/x) * Series_Reversion( x * sqrt(1 - 2*x*exp(x)) ).

Original entry on oeis.org

1, 1, 7, 87, 1621, 40485, 1271841, 48220207, 2143450009, 109350344745, 6298638659245, 404371344546411, 28633701543626037, 2217105596852342989, 186362307297569836993, 16901012222196104542695, 1644911203243501609414321, 171017059743998995011125457, 18916512667390427993433246357
Offset: 0

Views

Author

Seiichi Manyama, Jan 11 2025

Keywords

Crossrefs

Programs

  • PARI
    my(N=20, x='x+O('x^N)); Vec(serlaplace(serreverse(x*sqrt(1-2*x*exp(x)))/x))
    
  • PARI
    a(n) = n!*sum(k=0, n, 2^k*k^(n-k)*binomial(n/2+k+1/2, k)/((n+2*k+1)*(n-k)!));

Formula

E.g.f. A(x) satisfies A(x) = 1/sqrt( 1 - 2*x*A(x)*exp(x*A(x)) ).
a(n) = n! * Sum_{k=0..n} 2^k * k^(n-k) * binomial(n/2+k+1/2,k)/( (n+2*k+1)*(n-k)! ).
a(n) = (n!/(n+1)) * Sum_{k=0..n} (-2)^k * k^(n-k) * binomial(-n/2-1/2,k)/(n-k)!.
Showing 1-3 of 3 results.