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A189507 Triangle read by rows: T(n,k) (n >= 0, 1 <= k <= n+1) are the signed Hultman numbers. 7
1, 1, 1, 4, 3, 1, 20, 21, 6, 1, 148, 160, 65, 10, 1, 1348, 1620, 701, 155, 15, 1, 15104, 19068, 9324, 2247, 315, 21, 1, 198144, 264420, 138016, 38029, 5908, 574, 28, 1, 2998656, 4166880, 2325740, 692088, 124029, 13524, 966, 36, 1, 51290496, 74011488, 43448940, 13945700, 2723469, 344961, 27930, 1530, 45, 1, 979732224, 1459381440, 897020784, 305142068, 64711856, 8996295, 850905, 53262, 2310, 55 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

"Signed" refers to the fact that these numbers are associated with signed permutations. The numbers themselves are positive.

LINKS

Table of n, a(n) for n=0..64.

N. Alexeev, A. Pologova, M. A. Alekseyev, Generalized Hultman Numbers and Cycle Structures of Breakpoint Graphs, Journal of Computational Biology 24:2 (2017), 93-105. doi:10.1089/cmb.2016.0190 arXiv:1503.05285

Simona Grusea and Anthony Labarre, The distribution of cycles in breakpoint graphs of signed permutations, arXiv:1104.3353v1

EXAMPLE

Triangle begins:

1

1 1

4 3 1

20 21 6 1

148 160 65 10 1

1348 1620 701 155 15 1

15104 19068 9324 2247 315 21 1

...

CROSSREFS

The first three columns give A001171, A189508, A189509. Cf. A164652.

Sequence in context: A193795 A181355 A128320 * A208057 A298673 A245732

Adjacent sequences:  A189504 A189505 A189506 * A189508 A189509 A189510

KEYWORD

nonn,tabl

AUTHOR

N. J. A. Sloane, Apr 23 2011

STATUS

approved

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Last modified June 15 20:50 EDT 2019. Contains 324145 sequences. (Running on oeis4.)