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.

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

A354552 Expansion of e.g.f. exp( x * exp(x^4/24) ).

Original entry on oeis.org

1, 1, 1, 1, 1, 6, 31, 106, 281, 946, 7561, 54286, 281161, 1207636, 7997991, 81996916, 701522641, 4580581916, 29742355441, 306369616636, 3632198902321, 34710574441096, 276645112305871, 2652825718776696, 35647605796451881, 458142859493786776
Offset: 0

Views

Author

Seiichi Manyama, Aug 18 2022

Keywords

Comments

This sequence is different from A143568.

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(x*(exp(x^4/24)))))
    
  • PARI
    a(n) = n!*sum(k=0, n\4, (n-4*k)^k/(24^k*k!*(n-4*k)!));

Formula

a(n) = n! * Sum_{k=0..floor(n/4)} (n - 4*k)^k/(24^k * k! * (n - 4*k)!).

A367756 E.g.f. satisfies A(x) = exp(x * (1 + x + x^2 + x^3) * A(x^4/24)).

Original entry on oeis.org

1, 1, 3, 13, 73, 386, 2671, 20728, 175393, 1553968, 15520861, 165541806, 1869485773, 22249874518, 284029764383, 3804116563276, 53328350650081, 782331158754088, 12051288543702313, 193028133988081918, 3212490296905001781, 55543932173668760221
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\4+1]*v[i-j]/(24^(j\4)*(j\4)!*(i-1-j)!))); v;

Formula

a(0) = 1; a(n) = (n-1)! * Sum_{k=0..n-1} (k+1) * a(floor(k/4)) * a(n-1-k) / (24^floor(k/4) * floor(k/4)! * (n-1-k)!).
Showing 1-3 of 3 results.