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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A282988 Triangle of partitions of an n-set into boxes of size >= m.

Original entry on oeis.org

1, 2, 1, 5, 1, 1, 15, 4, 1, 1, 52, 11, 1, 1, 1, 203, 41, 11, 1, 1, 1, 877, 162, 36, 1, 1, 1, 1, 4140, 715, 92, 36, 1, 1, 1, 1, 21147, 3425, 491, 127, 1, 1, 1, 1, 1, 115975, 17722, 2557, 337, 127, 1, 1, 1, 1, 1, 678570, 98253, 11353, 793, 463, 1, 1, 1, 1, 1, 1
Offset: 1

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Author

Vladimir Kruchinin, Feb 26 2017

Keywords

Examples

			Triangle T(n,m) begins:
    1;
    2,   1;
    5,   1,   1;
   15,   4,   1,   1;
   52,  11,   1,   1,   1;
  203,  41,  11,   1,   1,   1;
  877, 162,  36,   1,   1,   1,   1;
  ...
		

Crossrefs

Programs

  • Maple
    T:= proc(n, k) option remember; `if`(n=0, 1, add(
          T(n-j, k)*binomial(n-1, j-1), j=k..n))
        end:
    seq(seq(T(n, k), k=1..n), n=1..14);  # Alois P. Heinz, Sep 28 2017
  • Mathematica
    T[n_, m_] := T[n, m] = Which[Or[n == m, n == 0], 1, m == 0, 0, True, Sum[Binomial[n - 1, i + m - 1] T[n - i - m, m], {i, 0, n - m}]]; Table[T[n, m], {n, 11}, {m, n}] // Flatten (* Michael De Vlieger, Feb 26 2017 *)
  • Maxima
    T(n,m):=if n=m or n=0 then 1 else if m=0 then 0 else sum(binomial(n-1, i+m-1)*T(n-i-m,m), i, 0, n-m);

Formula

T(n,m) = Sum_{i=0..n-m} C(n-1, i+m-1)*T(n-i-m, m).
E.g.f. m column of T(n,m) is exp(exp(x)-Sum_{k=0..m} 1/k!x^k).

A347435 E.g.f.: exp( exp(x) * (exp(x) - 1 - x - x^2 / 2 - x^3 / 6) ).

Original entry on oeis.org

1, 0, 0, 0, 1, 6, 22, 64, 198, 1138, 10004, 83920, 617993, 4226028, 30103686, 251883012, 2490287821, 26456763078, 281404300348, 2966101610920, 31877462564554, 362624252399566, 4437794875670072, 57612897938229380, 773900876490016325, 10599854900351622752
Offset: 0

Views

Author

Ilya Gutkovskiy, Sep 02 2021

Keywords

Comments

Exponential transform of A002663.

Crossrefs

Programs

  • Maple
    a:= proc(n) option remember; `if`(n=0, 1, add(
          a(n-j)*binomial(n-1, j-1)*(2^j-j^3/6-5*j/6-1), j=1..n))
        end:
    seq(a(n), n=0..25);  # Alois P. Heinz, Sep 02 2021
  • Mathematica
    nmax = 25; CoefficientList[Series[Exp[Exp[x] (Exp[x] - 1 - x - x^2/2 - x^3/6)], {x, 0, nmax}], x] Range[0, nmax]!
    a[0] = 1; a[n_] := a[n] = Sum[Binomial[n - 1, k - 1] (2^k - 1 - k (k^2 + 5)/6) a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 25}]

Formula

a(0) = 1; a(n) = Sum_{k=1..n} binomial(n-1,k-1) * A002663(k) * a(n-k).

A365894 Expansion of e.g.f. exp( Sum_{k>=0} x^(3*k+4) / (3*k+4)! ).

Original entry on oeis.org

1, 0, 0, 0, 1, 0, 0, 1, 35, 0, 1, 330, 5775, 1, 2717, 225225, 2627626, 21828, 6782490, 290990701, 2546343368, 190030590, 22939766851, 644182060203, 4514461227804, 1607617027501, 109664100094160, 2261215037103165, 13296854061626851, 15998661864449331
Offset: 0

Views

Author

Seiichi Manyama, Sep 22 2023

Keywords

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(sum(k=0, N\3, x^(3*k+4)/(3*k+4)!))))

Formula

a(0)=1; a(n) = Sum_{k=0..floor((n-4)/3)} binomial(n-1,3*k+3) * a(n-3*k-4).
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