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

Author

Joerg Arndt and Alois P. Heinz, Apr 28 2014

Keywords

• nonn

Examples

			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.