|
|
A319421
|
|
Triangle read by rows: T(n,k) (1 <= k <= n) = one-half of the number of binary vectors of length n and cuts-resistance k.
|
|
15
|
|
|
1, 1, 1, 1, 2, 1, 1, 4, 2, 1, 1, 6, 6, 2, 1, 1, 10, 11, 7, 2, 1, 1, 14, 24, 14, 8, 2, 1, 1, 22, 42, 35, 16, 9, 2, 1, 1, 30, 81, 68, 45, 18, 10, 2, 1, 1, 46, 138, 149, 89, 55, 20, 11, 2, 1, 1, 62, 250, 282, 216, 110, 66, 22, 12, 2, 1, 1, 94, 419, 577, 422, 285, 132, 78, 24, 13, 2, 1
(list;
table;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,5
|
|
COMMENTS
|
Cuts-resistance is defined in A319416.
This triangle summarizes the data shown in A319420.
Conjecture (Sloane): Sum_{i = 1..n} i * T(n,i) = A189391(n).
|
|
LINKS
|
Claude Lenormand, Deux transformations sur les mots, Preprint, 5 pages, Nov 17 2003. Apparently unpublished. This is a scanned copy of the version that the author sent to me in 2003. See page 4.
N. J. A. Sloane, Coordination Sequences, Planing Numbers, and Other Recent Sequences (II), Experimental Mathematics Seminar, Rutgers University, Jan 31 2019, Part I, Part 2, Slides. (Mentions this sequence)
|
|
FORMULA
|
|
|
EXAMPLE
|
Triangle begins:
1
1 1
1 2 1
1 4 2 1
1 6 6 2 1
1 10 11 7 2 1
1 14 24 14 8 2 1
1 22 42 35 16 9 2 1
1 30 81 68 45 18 10 2 1
1 46 138 149 89 55 20 11 2 1
1 62 250 282 216 110 66 22 12 2 1
1 94 419 577 422 285 132 78 24 13 2 1
Lenormand gives first 15 rows.
For example, the "1,2,1" row here refers to the 8 vectors of length 3. There are 2 vectors of cuts-resistance 1, namely 010 and 101 (see A319416), 4 vectors of cuts-resistance 2 (100,011,001,110), and 2 of cuts-resistance 3 (000 and 111). Halving these counts we get 1,2,1
|
|
MATHEMATICA
|
degdep[q_]:=Length[NestWhileList[Join@@Rest/@Split[#]&, q, Length[#]>0&]]-1;
Table[Length[Select[Tuples[{0, 1}, n], First[#]==1&°dep[#]==k&]], {n, 8}, {k, n}] (* Gus Wiseman, Nov 25 2019 *)
|
|
CROSSREFS
|
Column k = 2 appears to be A027383.
The version for compositions is A329861.
The cuts-resistance of the binary expansion of n is A319416(n).
|
|
KEYWORD
|
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|