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A367656
G.f. A(x) satisfies A(x) = 1 / (1 - x - x * (1 + x + x^2) * A(x^3)).
4
1, 2, 5, 13, 35, 94, 252, 678, 1823, 4900, 13176, 35427, 95250, 256105, 688599, 1851450, 4978062, 13384681, 35987808, 96761612, 260166110, 699517054, 1880814358, 5057006914, 13596939262, 36558534049, 98296122593, 264291989596, 710610490247, 1910641595588
OFFSET
0,2
FORMULA
a(0) = 1; a(n) = a(n-1) + Sum_{k=0..n-1} a(floor(k/3)) * a(n-1-k).
PROG
(PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=v[i]+sum(j=0, i-1, v[j\3+1]*v[i-j])); v;
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Nov 26 2023
STATUS
approved