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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A318105 Triangle read by rows: T(n,k) = (4*n - 3*k)!/((n-k)!^4*k!).

Original entry on oeis.org

1, 24, 1, 2520, 120, 1, 369600, 22680, 360, 1, 63063000, 4804800, 113400, 840, 1, 11732745024, 1072071000, 33633600, 415800, 1680, 1, 2308743493056, 246387645504, 9648639000, 168168000, 1247400, 3024, 1, 472518347558400, 57718587326400, 2710264100544, 61108047000, 672672000, 3243240, 5040, 1
Offset: 0

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Author

Gheorghe Coserea, Oct 15 2018

Keywords

Comments

Diagonal of rational function R(x,y,z,w,t) = 1/(1 - (x+y+z+w + t*x*y*z*w)) with respect to x,y,z,w, i.e., T(n,k) = [(xyzw)^n*t^k] R(x,y,z,w,t).
Annihilating differential operator: x^2*(3*t*x + 1)^2*((t*x - 1)^4 - 256*x)*Dx^3 + 3*x*(3*t*x + 1)*((t*x - 1)^3*(6*t^2*x^2 + 3*t*x - 1) - 384*x*(t*x + 1))*Dx^2 + (t*x - 1)*((t*x - 1)*(63*t^4*x^4 + 66*t^3*x^3 - 18*t*x + 1) + 48*x*(15*t*x + 17))*Dx + (t*x - 1)*(t*(9*t^4*x^4 + 12*t^3*x^3 + 6*t^2*x^2 - 12*t*x + 1) - 24*(15*t*x - 1)).

Examples

			A(x;t) = 1 + (24 + t)*x + (2520 + 120*t + t^2)*x^2 + (369600 + 22680*t + 360*t^2 + t^3)*x^3 + ...
Triangle starts:
n\k [0]            [1]           [2]         [3]        [4]      [5]   [6]
[0] 1;
[1] 24,            1;
[2] 2520,          120,          1;
[3] 369600,        22680,        360,        1;
[4] 63063000,      4804800,      113400,     840,       1;
[5] 11732745024,   1072071000,   33633600,   415800,    1680,    1;
[6] 2308743493056, 246387645504, 9648639000, 168168000, 1247400, 3024, 1;
[7] ...
		

Crossrefs

Programs

  • Mathematica
    t[n_,k_] := (4*n - 3*k)!/((n-k)!^4*k!); Table[t[n, k], {n, 0, 10}, {k , 0,n}] // Flatten  (* Amiram Eldar, Nov 07 2018 *)
  • PARI
    T(n, k) = (4*n-3*k)!/(k!*(n-k)!^4);
    concat(vector(8, n, vector(n, k, T(n-1, k-1))))
    /*
    test:
    P(n, v='t) = subst(Polrev(vector(n+1, k, T(n, k-1)), 't), 't, v);
    diag(expr, N=22, var=variables(expr)) = {
      my(a = vector(N));
      for (k = 1, #var, expr = taylor(expr, var[#var - k + 1], N));
      for (n = 1, N, a[n] = expr;
        for (k = 1, #var, a[n] = polcoef(a[n], n-1)));
      return(a);
    };
    apply_diffop(p, s) = {
      s=intformal(s);
      sum(n=0, poldegree(p, 'Dx), s=s'; polcoef(p, n, 'Dx) * s);
    };
    \\ diagonal property:
    x='x; y='y; z='z; w='w; t='t;
    diag(1/(1 - (x+y+z+w + t*x*y*z*w)), 9, [x, y, z, w]) == vector(9, n, P(n-1))
    \\ annihilating diffop:
    y = Ser(vector(101, n, P(n-1)), 'x);
    p = x^2*(3*t*x + 1)^2*((t*x - 1)^4 - 256*x)*Dx^3 + 3*x*(3*t*x + 1)*((t*x - 1)^3*(6*t^2*x^2 + 3*t*x - 1) - 384*x*(t*x + 1))*Dx^2 + (t*x - 1)*((t*x - 1)*(63*t^4*x^4 + 66*t^3*x^3 - 18*t*x + 1) + 48*x*(15*t*x + 17))*Dx + (t*x - 1)*(t*(9*t^4*x^4 + 12*t^3*x^3 + 6*t^2*x^2 - 12*t*x + 1) - 24*(15*t*x - 1));
    0 == apply_diffop(p, y)
    */

Formula

Let P_n(t) = Sum_{k=0..n} T(n,k)*t^k. Then A125143(n) = P_n(-27), A008977(n) = P_n(0), A082488(n) = P_n(1).
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