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A373655
a(n) = Sum_{k=0..floor(n/3)} binomial(3*n-8*k-1,k).
0
1, 1, 1, 1, 4, 7, 10, 19, 37, 64, 110, 201, 364, 641, 1140, 2050, 3662, 6516, 11638, 20811, 37140, 66268, 118356, 211368, 377308, 673605, 1202805, 2147563, 3834121, 6845572, 12222605, 21822509, 38962178, 69564612, 124203381, 221756004, 395929588, 706906325
OFFSET
0,5
FORMULA
G.f.: 1 / (1 - x/(1 - x^3)^3).
a(n) = a(n-1) + 3*a(n-3) - 3*a(n-6) + a(n-9) for n > 9.
PROG
(PARI) a(n) = sum(k=0, n\3, binomial(3*n-8*k-1, k));
CROSSREFS
Cf. A373640.
Sequence in context: A161334 A111981 A338130 * A080922 A227686 A161863
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Jun 12 2024
STATUS
approved