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.

Previous Showing 11-13 of 13 results.

A288790 Number of blocks of size >= eight in all set partitions of n.

Original entry on oeis.org

1, 10, 101, 947, 8670, 79249, 730745, 6838642, 65197797, 634656360, 6316333291, 64318009411, 670336612614, 7151290120037, 78085166445577, 872478836270306, 9972817907218608, 116575837400037486, 1393037460835481622, 17010118386233081680, 212160149063581345610
Offset: 8

Views

Author

Alois P. Heinz, Jun 15 2017

Keywords

Crossrefs

Column k=8 of A283424.
Cf. A000110.

Programs

  • Maple
    b:= proc(n) option remember; `if`(n=0, 1, add(
          b(n-j)*binomial(n-1, j-1), j=1..n))
        end:
    g:= proc(n, k) option remember; `if`(n g(n, 8):
    seq(a(n), n=8..30);
  • Mathematica
    Table[Sum[Binomial[n, j] BellB[j], {j, 0, n - 8}], {n, 8, 30}] (* Indranil Ghosh, Jul 06 2017 *)
  • Python
    from sympy import bell, binomial
    def a(n): return sum(binomial(n, j)*bell(j) for j in range(n - 7))
    print([a(n) for n in range(8, 31)]) # Indranil Ghosh, Jul 06 2017

Formula

a(n) = Bell(n+1) - Sum_{j=0..7} binomial(n,j) * Bell(n-j).
a(n) = Sum_{j=0..n-8} binomial(n,j) * Bell(j).
E.g.f.: (exp(x) - Sum_{k=0..7} x^k/k!) * exp(exp(x) - 1). - Ilya Gutkovskiy, Jun 26 2022

A288791 Number of blocks of size >= nine in all set partitions of n.

Original entry on oeis.org

1, 11, 122, 1245, 12325, 121136, 1195147, 11915997, 120572790, 1241499241, 13030331671, 139549798524, 1525923634907, 17041290249637, 194394900237176, 2264977282222371, 26951265841776186, 327445918493429897, 4060993235341162405, 51396034231430455550
Offset: 9

Views

Author

Alois P. Heinz, Jun 15 2017

Keywords

Crossrefs

Column k=9 of A283424.
Cf. A000110.

Programs

  • Maple
    b:= proc(n) option remember; `if`(n=0, 1, add(
          b(n-j)*binomial(n-1, j-1), j=1..n))
        end:
    g:= proc(n, k) option remember; `if`(n g(n, 9):
    seq(a(n), n=9..30);
  • Mathematica
    Table[Sum[Binomial[n, j] BellB[j], {j, 0, n - 9}], {n, 9, 30}] (* Indranil Ghosh, Jul 06 2017 *)
  • Python
    from sympy import bell, binomial
    def a(n): return sum([binomial(n, j)*bell(j) for j in range(n - 8)])
    print([a(n) for n in range(9, 31)]) # Indranil Ghosh, Jul 06 2017

Formula

a(n) = Bell(n+1) - Sum_{j=0..8} binomial(n,j) * Bell(n-j).
a(n) = Sum_{j=0..n-9} binomial(n,j) * Bell(j).
E.g.f.: (exp(x) - Sum_{k=0..8} x^k/k!) * exp(exp(x) - 1). - Ilya Gutkovskiy, Jun 26 2022

A288792 Number of blocks of size >= ten in all set partitions of n.

Original entry on oeis.org

1, 12, 145, 1600, 17032, 179132, 1883117, 19929390, 213332101, 2316793121, 25577181324, 287421068697, 3290394397097, 38393883291996, 456753452800691, 5540597439008861, 68530489547341697, 864218608315007230, 11109867095322262250, 145563654356205885737
Offset: 10

Views

Author

Alois P. Heinz, Jun 15 2017

Keywords

Crossrefs

Column k=10 of A283424.
Cf. A000110.

Programs

  • Maple
    b:= proc(n) option remember; `if`(n=0, 1, add(
          b(n-j)*binomial(n-1, j-1), j=1..n))
        end:
    g:= proc(n, k) option remember; `if`(n g(n, 10):
    seq(a(n), n=10..30);
  • Mathematica
    Table[Sum[Binomial[n, j] BellB[j], {j, 0, n - 10}], {n, 10, 30}] (* Indranil Ghosh, Jul 06 2017 *)
  • Python
    from sympy import bell, binomial
    def a(n): return sum([binomial(n, j)*bell(j) for j in range(n - 9)])
    print([a(n) for n in range(10, 31)]) # Indranil Ghosh, Jul 06 2017

Formula

a(n) = Bell(n+1) - Sum_{j=0..9} binomial(n,j) * Bell(n-j).
a(n) = Sum_{j=0..n-10} binomial(n,j) * Bell(j).
E.g.f.: (exp(x) - Sum_{k=0..9} x^k/k!) * exp(exp(x) - 1). - Ilya Gutkovskiy, Jun 26 2022
Previous Showing 11-13 of 13 results.