login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A261781 Number T(n,k) of compositions of n where each part i is marked with a word of length i over a k-ary alphabet whose letters appear in alphabetical order and all k letters occur at least once in the composition; triangle T(n,k), n >= 0, 0 <= k <= n, read by rows. 17
1, 0, 1, 0, 2, 3, 0, 4, 16, 13, 0, 8, 66, 132, 75, 0, 16, 248, 924, 1232, 541, 0, 32, 892, 5546, 13064, 13060, 4683, 0, 64, 3136, 30720, 114032, 195020, 155928, 47293, 0, 128, 10888, 162396, 893490, 2327960, 3116220, 2075948, 545835 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

From Vaclav Kotesovec, Oct 14 2017: (Start)

Conjecture: For k > 0 the recurrence order for column k is equal to k*(k+1)/2.

Column k > 0 is asymptotic to c(k) * d(k)^n, where c(k) and d(k) are constants (dependent only on k).

k                           c(k)                            d(k)

1  A131577(n) ~ 0.50000000000000000000000000 * 2.00000000000000000000000000^n.

2  A293579(n) ~ 0.60355339059327376220042218 * 3.41421356237309504880168872^n.

3  A293580(n) ~ 0.64122035031051210658648604 * 4.84732210186307263951891624^n.

4  A293581(n) ~ 0.66065168848540565019767995 * 6.28521350788324520158143964^n.

5  A293582(n) ~ 0.67250239588725756267924287 * 7.72502395887257562679242875^n.

6  A293583(n) ~ 0.68048292906885160660288253 * 9.16579514882621927923459043^n.

7  A293584(n) ~ 0.68622254929933439577377124 * 10.6071156901906815408327973^n.

8  A293585(n) ~ 0.69054873168854973836384871 * 12.0487797070167958138215794^n.

9  A293586(n) ~ 0.69392626461456654033893782 * 13.4906727630621977261008808^n.

10 A293587(n) ~ 0.69663630864564830007443110 * 14.9327261729129660014886221^n.

---

Conjecture: d(k+1) - d(k) tends to 1/log(2).

d(2) - d(1) = 1.414213562373095048801688724209698...

d(3) - d(2) = 1.433108539489977590717227522340838...

d(4) - d(3) = 1.437891406020172562062523400686067...

d(5) - d(4) = 1.439810450989330425210989107036901...

d(6) - d(5) = 1.440771189953643652442161677346934...

d(7) - d(6) = 1.441320541364462261598206961226199...

d(8) - d(7) = 1.441664016826114272988782079622148...

d(9) - d(8) = 1.441893056045401912279301345910755...

d(10)- d(9) = 1.442053409850768275387741352145193...

1 / log(2)  = 1.442695040888963407359924681001892...

(End)

LINKS

Alois P. Heinz, Rows n = 0..140, flattened

E. Munarini, M. Poneti, S. Rimaldi, Matrix compositions, JIS 12 (2009) 09.4.8, Table 2.

FORMULA

T(n,k) = Sum_{i=0..k} (-1)^i * C(k,i) * A261780(n,k-i).

EXAMPLE

A(3,2) = 16: 3aab, 3abb, 2aa1b, 2ab1a, 2ab1b, 2bb1a, 1a2ab, 1a2bb, 1b2aa, 1b2ab, 1a1a1b, 1a1b1a, 1a1b1b, 1b1a1a, 1b1a1b, 1b1b1a.

Triangle T(n,k) begins:

  1;

  0,  1;

  0,  2,    3;

  0,  4,   16,    13;

  0,  8,   66,   132,     75;

  0, 16,  248,   924,   1232,    541;

  0, 32,  892,  5546,  13064,  13060,   4683;

  0, 64, 3136, 30720, 114032, 195020, 155928, 47293;

MAPLE

A:= proc(n, k) option remember; `if`(n=0, 1,

      add(A(n-j, k)*binomial(j+k-1, k-1), j=1..n))

    end:

T:= (n, k)-> add(A(n, k-i)*(-1)^i*binomial(k, i), i=0..k):

seq(seq(T(n, k), k=0..n), n=0..10);

MATHEMATICA

A[n_, k_] := A[n, k] = If[n==0, 1, Sum[A[n-j, k]*Binomial[j+k-1, k-1], {j, 1, n}]]; T[n_, k_] := Sum[A[n, k-i]*(-1)^i*Binomial[k, i], {i, 0, k}]; Table[T[n, k], {n, 0, 10}, {k, 0, n}] // Flatten (* Jean-Fran├žois Alcover, Feb 08 2017, translated from Maple *)

CROSSREFS

Columns k=0..10 give A000007, A131577, A293579, A293580, A293581, A293582, A293583, A293584, A293585, A293586, A293587.

Row sums give A120733.

Main diagonal gives A000670.

T(2n,n) gives A261784.

T(n+1,n)/2 gives A083385.

Cf. A261719 (same for partitions), A261780.

Sequence in context: A258818 A261275 A140326 * A211402 A256064 A126436

Adjacent sequences:  A261778 A261779 A261780 * A261782 A261783 A261784

KEYWORD

nonn,tabl

AUTHOR

Alois P. Heinz, Aug 31 2015

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 16 21:37 EST 2020. Contains 331975 sequences. (Running on oeis4.)