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).

A276841 Number of permutations of [n] such that for each cycle c the smallest integer interval containing all elements of c has at most seven elements.

Original entry on oeis.org

1, 1, 2, 6, 24, 120, 720, 5040, 20160, 75600, 287280, 1133550, 4686660, 20368569, 93109737, 406088940, 1719126780, 7184340564, 29966843736, 125593803792, 530881463680, 2267064321984, 9681953067016, 41200660295772, 174712473986620, 739333708856220
Offset: 0

Views

Author

Alois P. Heinz, Sep 20 2016

Keywords

Crossrefs

Column k=7 of A276837.
Cf. A276723.

Formula

G.f.: -(x^52 +6*x^50 -34*x^49 +20*x^48 +482*x^47 -426*x^46 -1468*x^45 -4536*x^44 +3648*x^43 +19218*x^42 +980*x^41 +11510*x^40 -47116*x^39 +35786*x^38 +93064*x^37 +164632*x^36 +300102*x^35 -85560*x^34 -604736*x^33 +93922*x^32 -445966*x^31 +372558*x^30 +156416*x^29 +160198*x^28 -518168*x^27 -147664*x^26 -493240*x^25 +29594*x^24 +313562*x^23 +610220*x^22 +32062*x^21 -12854*x^20 +13220*x^19 -157960*x^18 -46776*x^17 -70050*x^16 -41076*x^15 -50710*x^14 -5996*x^13 +1894*x^12 -1936*x^11 +968*x^10 +738*x^9 +1040*x^8 +776*x^7 -2*x^6 +70*x^5 +34*x^4 +8*x^3 +2*x^2 -1) / (x^64 +11*x^63 +15*x^62 -31*x^61 +21*x^60 -881*x^59 +6397*x^58 +41653*x^57 +32901*x^56 -67903*x^55 -284725*x^54 -392391*x^53 +559947*x^52 +104334*x^51 -1200042*x^50 -2062678*x^49 -1572286*x^48 +15473434*x^47 +15863554*x^46 +35936394*x^45 +69616662*x^44 -80992842*x^43 -307844474*x^42 -283307502*x^41 -219491322*x^40 +338286*x^39 +213380440*x^38 -3315412*x^37 -349666888*x^36 -484336364*x^35 -431418124*x^34 -248674504*x^33 +22949740*x^32 +144629920*x^31 -9726680*x^30 -113690432*x^29 -126317520*x^28 -143609200*x^27 -79336148*x^26 +10701066*x^25 -42072302*x^24 -78959890*x^23 -72447322*x^22 -22061410*x^21 -5812154*x^20 -8720370*x^19 -2145534*x^18 +2011058*x^17 +2823538*x^16 +1655238*x^15 +661954*x^14 +294538*x^13 +118975*x^12 +23793*x^11 -13327*x^10 -11405*x^9 -7057*x^8 -3807*x^7 -305*x^6 -93*x^5 -37*x^4 -9*x^3 -3*x^2 -x +1).

A276897 Number of ordered set partitions of [n] such that for each block b the smallest integer interval containing b has at most seven elements.

Original entry on oeis.org

1, 1, 3, 13, 75, 541, 4683, 47293, 498542, 5586952, 67067528, 863967424, 11931711152, 176258744536, 2777402228132, 46453613044464, 821540685443328, 15314758450069728, 300131246157443016, 6169170736959823656, 132727347264381285042, 2983326113743943646918
Offset: 0

Views

Author

Alois P. Heinz, Sep 21 2016

Keywords

Crossrefs

Column k=7 of A276890.
Cf. A276723.

Formula

a(n) ~ exp(6) * n!. - Vaclav Kotesovec, Sep 22 2016

A320557 Number of set partitions of [n] such that for each block b the smallest integer interval containing b has at most seven elements and for at least one block c the smallest integer interval containing c has exactly seven elements.

Original entry on oeis.org

203, 1197, 4971, 18223, 63768, 220419, 779242, 2845864, 10418560, 37768970, 135153976, 477964329, 1676343822, 5852483376, 20403590238, 71080014610, 247360604490, 859493636214, 2980904955378, 10318666659192, 35656973487023, 123042978647274, 424121272321296
Offset: 7

Views

Author

Alois P. Heinz, Oct 15 2018

Keywords

Crossrefs

Column k=7 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)))(7):
    seq(a(n), n=7..50);

Formula

a(n) = A276723(n) - A276722(n).

A320558 Number of set partitions of [n] such that for each block b the smallest integer interval containing b has at most eight elements and for at least one block c the smallest integer interval containing c has exactly eight elements.

Original entry on oeis.org

877, 5852, 27267, 110545, 422396, 1578192, 5877165, 22355618, 87597223, 345223398, 1352883364, 5249340393, 20158426185, 76729396494, 290259302392, 1094289866107, 4121529511428, 15518374075986, 58402401729381, 219602989556557, 824720185307142, 3092742982300231
Offset: 8

Views

Author

Alois P. Heinz, Oct 15 2018

Keywords

Crossrefs

Column k=8 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)))(8):
    seq(a(n), n=8..50);

Formula

a(n) = A276724(n) - A276723(n).
Showing 1-5 of 5 results.