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A026134
a(n) = Sum_{k=1..n} T(k, k-1), where T is the array in A026120.
3
1, 2, 6, 16, 44, 120, 329, 904, 2493, 6898, 19151, 53340, 149019, 417522, 1172979, 3303696, 9326931, 26390070, 74824584, 212565864, 604972998, 1724739940, 4925066567, 14085122376, 40339596755, 115688495806, 332203673142, 955090832416, 2749055259956, 7921280088744
OFFSET
1,2
FORMULA
G.f.: z(1-z)M^3, with M the g.f. of the Motzkin numbers (A001006).
CROSSREFS
T(n, n+2), where T is given by A026148, T(n, n-2), where T is the array defined in A026105 and T(n, n+1), where T is given by A026323.
First differences of A005322.
Cf. A026123.
Sequence in context: A118041 A105073 A002605 * A105696 A074413 A373048
KEYWORD
nonn
EXTENSIONS
a(25) corrected and more terms from Sean A. Irvine, Sep 17 2019
STATUS
approved