A241797 Number of ballot sequences of length n having exactly four descents.

9, 146, 1324, 8786, 47013, 214997, 874413, 3228005, 11049817, 35389760, 107476721, 310853113, 863984856, 2313084483, 6003120701, 15122836712, 37154716734, 89093938147, 209258012995, 481663102867, 1089445474512, 2422311605452, 5305675093522, 11451261202545

Offset

8,1

Links

Table of n, a(n) for n=8..31.

Example

a(8) = 9: [1,2,1,2,1,3,2,1], [1,2,1,3,1,4,2,1], [1,2,1,3,2,1,2,1], [1,2,1,3,2,1,3,1], [1,2,1,3,2,1,3,2], [1,2,1,3,2,1,4,1], [1,2,1,3,2,1,4,2], [1,2,1,3,2,1,4,3], [1,2,1,3,2,4,3,1].

Crossrefs

Column k=4 of A238121 and of A238122.

Sequence in context: A178185 A244822 A299319 * A222439 A211106 A006691

Adjacent sequences: A241794 A241795 A241796 * A241798 A241799 A241800

Keyword

nonn

Author

Joerg Arndt and Alois P. Heinz, Apr 28 2014

Status

approved