A367691 - OEIS

%I #9 Nov 27 2023 07:56:58

%S 1,2,3,4,7,12,19,31,52,86,141,233,386,639,1057,1749,2896,4795,7937,

%T 13138,21751,36010,59613,98688,163380,270479,447779,741300,1227231,

%U 2031697,3363494,5568295,9218373,15261119,25264942,41826373,69244006,114634194,189778123

%N G.f. A(x) satisfies A(x) = 1 / ((1 - x) * (1 - x * A(x^3))).

%F a(n) = 1 + Sum_{k=0..floor((n-1)/3)} a(k) * a(n-1-3*k).

%o (PARI) a_vector(n) = my(v=vector(n+1)); for(i=0, n, v[i+1]=1+sum(j=0, (i-1)\3, v[j+1]*v[i-3*j])); v;

%Y Cf. A007317, A351972, A367692.

%Y Cf. A367659.

%K nonn

%O 0,2

%A _Seiichi Manyama_, Nov 27 2023