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A291887
Number of symmetrically unique Dyck paths of semilength n and height three.
2
1, 3, 11, 31, 91, 250, 690, 1863, 5017, 13389, 35621, 94354, 249352, 657421, 1730685, 4550031, 11950963, 31365810, 82274126, 215711947, 565376593, 1481448697, 3881041065, 10165822434, 26624745964, 69725071281, 182583838181, 478093234315, 1251829592839
OFFSET
3,2
LINKS
FORMULA
G.f.: -x^3*(x^4+2*x^2-3*x+1)/((2*x-1)*(x^2-3*x+1)*(2*x^2-1)*(x^2+x-1)).
CROSSREFS
Column k=3 of A291883.
Sequence in context: A320238 A369399 A108898 * A217323 A263781 A119901
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Sep 05 2017
STATUS
approved