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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A143565 Triangle T(n,k), n>=1, 1<=k<=n, where the e.g.f. for column k satisfies: A_k(x) = exp(x*A_k(x^k/k!)).

Original entry on oeis.org

1, 3, 1, 16, 4, 1, 125, 13, 5, 1, 1296, 46, 21, 6, 1, 16807, 241, 61, 31, 7, 1, 262144, 1471, 211, 106, 43, 8, 1, 4782969, 9409, 1401, 281, 169, 57, 9, 1, 100000000, 67348, 8065, 946, 505, 253, 73, 10, 1, 2357947691, 564841, 37241, 7561, 1261, 841, 361, 91, 11, 1
Offset: 1

Views

Author

Alois P. Heinz, Aug 24 2008

Keywords

Examples

			Triangle begins:
       1;
       3,    1;
      16,    4,    1;
     125,   13,    5,    1;
    1296,   46,   21,    6,    1;
   16807,  241,   61,   31,    7,    1;
  262144, 1471,  211,  106,   43,    8,    1;
  ...
		

Crossrefs

Programs

  • Maple
    A:= proc(n,k::posint) option remember; if n<=0 then 1 else unapply(
          convert(series(exp(x*A(n-k,k)(x^k/k!)), x,n+1), polynom),x) fi
        end:
    T:= (n,k)-> coeff(A(n,k)(x), x,n)*n!:
    seq(seq(T(n,k), k=1..n), n=1..12);
  • Mathematica
    a[n_, k_] := a[n, k] = If[n <= 0, 1&, Function[x, Series[E^(x*a[n - k, k][x^k/k!]), {x, 0, n+1}] // Normal // Evaluate]]; t[n_, k_] := Coefficient[a[n, k][x], x, n]*n!; Flatten[Table[Table[t[n, k], {k, 1, n}], {n, 1, 12}]] (* Jean-François Alcover, Dec 16 2013, translated from Maple *)

Formula

E.g.f. for column k satisfies: A_k(x) = exp(x*A_k(x^k/k!)).
T(0,k) = 1; T(n,k) = (n-1)! * Sum_{j=0..floor((n-1)/k)} (k*j+1) * T(j,k) * T(n-1-k*j,k) / (k!^j * j! * (n-1-k*j)!). - Seiichi Manyama, Nov 28 2023

A367757 E.g.f. satisfies A(x) = exp(x * (1 + x + x^2 + x^3 + x^4) * A(x^5/120)).

Original entry on oeis.org

1, 1, 3, 13, 73, 501, 3337, 27637, 254409, 2557369, 27603631, 313768731, 3905502745, 51573777841, 718307494269, 10507900625251, 161239887204721, 2608009648536417, 43989477103304155, 772109936171046001, 14085074476090366761, 266890182641557777093
Offset: 0

Views

Author

Seiichi Manyama, Nov 29 2023

Keywords

Crossrefs

Programs

  • PARI
    a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=(i-1)!*sum(j=0, i-1, (j+1)*v[j\5+1]*v[i-j]/(120^(j\5)*(j\5)!*(i-1-j)!))); v;

Formula

a(0) = 1; a(n) = (n-1)! * Sum_{k=0..n-1} (k+1) * a(floor(k/5)) * a(n-1-k) / (120^floor(k/5) * floor(k/5)! * (n-1-k)!).
Showing 1-2 of 2 results.