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.

A344849 a(n) is the numerator of Catalan-Daehee number d(n).

Original entry on oeis.org

1, 1, 7, 20, 313, 344, 24634, 86008, 183349, 3301264, 132174038, 69326344, 3332927794, 17361255440, 108222173516, 406589577424, 26070625295573, 8970328188896, 55462481190898, 1055714050810664, 2169454884422962, 91277283963562352, 8046203518285051612, 686567135431420560
Offset: 0

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Author

Stefano Spezia, May 30 2021

Keywords

Crossrefs

Cf. A000108, A000302, A014973 (denominators of Daehee numbers), A343206, A344850 (denominators).

Programs

  • Mathematica
    nmax:=24; a[n_]:=Numerator[Coefficient[Series[Log[1-4x]/(2(Sqrt[1-4x]-1)),{x,0,nmax}],x,n]]; Array[a,nmax,0] (* or *)
    a[n_]:=Numerator[If[n==0,1,4^n/(n+1)-Sum[4^(n-m-1)CatalanNumber[m]/(n-m),{m,0,n-1}]]]; Array[a,24,0]

Formula

G.f. of d(n): log(1 - 4*x)/(2*(sqrt(1 - 4*x) - 1)).
a(n) = numerator(d(n)), where d(n) = 4^n/(n + 1) - Sum_{m=0..n-1} 4^(n-m-1)*C(m)/(n - m) with d(0) = 1 and C(m) is the m-th Catalan number.