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A241797
Number of ballot sequences of length n having exactly four descents.
2
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
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
KEYWORD
nonn
AUTHOR
Joerg Arndt and Alois P. Heinz, Apr 28 2014
STATUS
approved