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 1-5 of 5 results.

A276719 Number A(n,k) of set partitions of [n] such that for each block b the smallest integer interval containing b has at most k elements; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 2, 1, 0, 1, 1, 2, 3, 1, 0, 1, 1, 2, 5, 5, 1, 0, 1, 1, 2, 5, 10, 8, 1, 0, 1, 1, 2, 5, 15, 20, 13, 1, 0, 1, 1, 2, 5, 15, 37, 42, 21, 1, 0, 1, 1, 2, 5, 15, 52, 87, 87, 34, 1, 0, 1, 1, 2, 5, 15, 52, 151, 208, 179, 55, 1, 0, 1, 1, 2, 5, 15, 52, 203, 409, 515, 370, 89, 1, 0
Offset: 0

Views

Author

Alois P. Heinz, Sep 16 2016

Keywords

Comments

The sequence of column k satisfies a linear recurrence with constant coefficients of order 2^(k-1) for k>0.

Examples

			A(3,2) = 3: 12|3, 1|23, 1|2|3.
A(4,3) = 10: 123|4, 12|34, 12|3|4, 13|24, 13|2|4, 1|234, 1|23|4, 1|24|3, 1|2|34, 1|2|3|4.
A(5,4) = 37: 1234|5, 123|45, 123|4|5, 124|35, 124|3|5, 12|345, 12|34|5, 12|35|4, 12|3|45, 12|3|4|5, 134|25, 134|2|5, 13|245, 13|24|5, 13|25|4, 13|2|45, 13|2|4|5, 14|235, 14|23|5, 1|2345, 1|234|5, 1|235|4, 1|23|45, 1|23|4|5, 14|25|3, 14|2|35, 14|2|3|5, 1|245|3, 1|24|35, 1|24|3|5, 1|25|34, 1|2|345, 1|2|34|5, 1|25|3|4, 1|2|35|4, 1|2|3|45, 1|2|3|4|5.
Square array A(n,k) begins:
  1, 1,  1,   1,   1,    1,    1,    1,    1, ...
  0, 1,  1,   1,   1,    1,    1,    1,    1, ...
  0, 1,  2,   2,   2,    2,    2,    2,    2, ...
  0, 1,  3,   5,   5,    5,    5,    5,    5, ...
  0, 1,  5,  10,  15,   15,   15,   15,   15, ...
  0, 1,  8,  20,  37,   52,   52,   52,   52, ...
  0, 1, 13,  42,  87,  151,  203,  203,  203, ...
  0, 1, 21,  87, 208,  409,  674,  877,  877, ...
  0, 1, 34, 179, 515, 1100, 2066, 3263, 4140, ...
		

Crossrefs

Main diagonal gives A000110.
A(n+1,n) gives A005493(n-1) for n>0.

Programs

  • Maple
    b:= proc(n, m, l) option remember; `if`(n=0, 1,
          add(b(n-1, max(m, j), [subsop(1=NULL, l)[],
          `if`(j<=m, 0, j)]), j={l[], m+1} minus {0}))
        end:
    A:= (n, k)-> `if`(n=0, 1, `if`(k<2, k, b(n, 0, [0$(k-1)]))):
    seq(seq(A(n, d-n), n=0..d), d=0..14);
  • Mathematica
    b[n_, m_, l_List] := b[n, m, l] = If[n == 0, 1, Sum[b[n - 1, Max[m, j], Append[ReplacePart[l, 1 -> Nothing], If[j <= m, 0, j]]], {j, Append[l, m + 1] ~Complement~ {0}}]]; A[n_, k_] := If[n == 0, 1, If[k < 2, k, b[n, 0, Array[0&, k-1]]]]; Table[A[n, d-n], {d, 0, 14}, {n, 0, d}] // Flatten (* Jean-François Alcover, Jan 06 2017, after Alois P. Heinz *)

Formula

A(n,k) = Sum_{i=0..k} A276727(n,i).

A276843 Number of permutations of [n] such that for each cycle c the smallest integer interval containing all elements of c has at most nine elements.

Original entry on oeis.org

1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 1814400, 8316000, 37920960, 176833800, 852972120, 4277399490, 22346336880, 121693555905, 690665206113, 3742590924108, 19625337285660, 101084160732660, 516806625700056, 2640952527095376, 13549247936670720
Offset: 0

Views

Author

Alois P. Heinz, Sep 20 2016

Keywords

Crossrefs

Column k=9 of A276837.
Cf. A276725.

A276899 Number of ordered set partitions of [n] such that for each block b the smallest integer interval containing b has at most nine elements.

Original entry on oeis.org

1, 1, 3, 13, 75, 541, 4683, 47293, 545835, 7087261, 95160302, 1336605832, 19761235784, 308372439520, 5082485111648, 88427826212320, 1622190325391504, 31329432209039896, 635929197472661444, 13526250938401091568, 300743675140836904032, 6975365075051730713856
Offset: 0

Views

Author

Alois P. Heinz, Sep 21 2016

Keywords

Crossrefs

Column k=9 of A276890.
Cf. A276725.

Formula

a(n) ~ exp(8) * n!. - Vaclav Kotesovec, Sep 22 2016

A320559 Number of set partitions of [n] such that for each block b the smallest integer interval containing b has at most nine elements and for at least one block c the smallest integer interval containing c has exactly nine elements.

Original entry on oeis.org

4140, 30751, 158766, 705926, 2928164, 11774145, 46852653, 186723275, 759062433, 3170429794, 13343960839, 56013146481, 233387096649, 963938933894, 3948441860748, 16062919807404, 65036845178255, 262641546675463, 1059920408695467, 4277149345637299
Offset: 9

Views

Author

Alois P. Heinz, Oct 15 2018

Keywords

Crossrefs

Column k=9 of A276727.

Programs

  • Maple
    b:= proc(n, m, l) option remember; `if`(n=0, 1,
          add(b(n-1, max(m, j), [subsop(1=NULL, l)[],
          `if`(j<=m, 0, j)]), j={l[], m+1} minus {0}))
        end:
    A:= (n, k)-> `if`(n=0, 1, `if`(k<2, k, b(n, 0, [0$(k-1)]))):
    a:= n-> (k-> A(n, k) -`if`(k=0, 0, A(n, k-1)))(9):
    seq(a(n), n=9..40);

Formula

a(n) = A276725(n) - A276724(n).

A320560 Number of set partitions of [n] such that for each block b the smallest integer interval containing b has at most ten elements and for at least one block c the smallest integer interval containing c has exactly ten elements.

Original entry on oeis.org

21147, 172649, 977607, 4732307, 21196160, 91356135, 387221998, 1635077589, 6933701115, 29953216031, 132647186513, 592562183163, 2645622362009, 11748752847703, 51794376799161, 226629372792025, 984996790932516, 4257860514411454, 18336632254191876
Offset: 10

Views

Author

Alois P. Heinz, Oct 15 2018

Keywords

Crossrefs

Column k=10 of A276727.

Programs

  • Maple
    b:= proc(n, m, l) option remember; `if`(n=0, 1,
          add(b(n-1, max(m, j), [subsop(1=NULL, l)[],
          `if`(j<=m, 0, j)]), j={l[], m+1} minus {0}))
        end:
    A:= (n, k)-> `if`(n=0, 1, `if`(k<2, k, b(n, 0, [0$(k-1)]))):
    a:= n-> (k-> A(n, k) -`if`(k=0, 0, A(n, k-1)))(10):
    seq(a(n), n=10..40);

Formula

a(n) = A276726(n) - A276725(n).
Showing 1-5 of 5 results.