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 1-1 of 1 results.

A181088 a(n) = A181089(2*n+1,n)/(n+2).

Original entry on oeis.org

1, -4, -40, 672, 8064, -253440, -3294720, 153753600, 2091048960, -130025226240, -1820353167360, 141707492720640, 2024392753152000, -189483161695027200, -2747505844577894400, 300609462994993152000, 4408938790593232896000
Offset: 0

Views

Author

Roger L. Bagula, Oct 02 2010

Keywords

Comments

What are the constraints on left-right symmetric triangles t(n,m) such that t(2*n,n)/(n+1) are integers?

Crossrefs

Programs

  • Mathematica
    (* First program *)
    p[x_, n_] = HermiteH[n, x] + ExpandAll[x^n*HermiteH[n, 1/x]];
    b:= Table[CoefficientList[p[x, n], x], {n, 0, 50}];
    Table[b[[2*n+2, n+1]]/(n+2), {n,0,20}]
    (* Second program *)
    A060821[n_, k_]:= If[EvenQ[n-k], (-1)^(Floor[(n-k)/2])*2^k*n!/(k!*(Floor[(n - k)/2]!)), 0];
    a[n_]:= (A060821[2*n+1, n] + A060821[2*n+1, n+1])/(n+2);
    Table[a[n], {n, 0, 25}] (* G. C. Greubel, Apr 04 2021 *)
  • Sage
    def A060821(n,k): return (-1)^((n-k)//2)*2^k*factorial(n)/(factorial(k)*factorial( (n-k)//2)) if (n-k)%2==0 else 0
    def a(n): return (A060821(2*n+1, n) + A060821(2*n+1, n+1))/(n+2)
    [a(n) for n in (0..25)] # G. C. Greubel, Apr 04 2021

Formula

a(n) = (A060821(2*n+1, n) + A060821(2*n+1, n+1))/(n+2). - G. C. Greubel, Apr 04 2021
Showing 1-1 of 1 results.