A366646 - OEIS

%I #10 Oct 15 2023 09:26:05

%S 1,0,0,0,1,4,10,20,39,88,228,600,1507,3652,8866,22100,56365,144656,

%T 369784,942480,2408934,6196280,16026652,41571640,107959654,280708560,

%U 731349400,1910098320,4999759830,13109582376,34421585844,90500370760,238272324682

%N G.f. A(x) satisfies A(x) = 1 + (x * A(x) / (1 - x))^4.

%F a(n) = Sum_{k=0..floor(n/4)} binomial(n-1,n-4*k) * binomial(4*k,k) / (3*k+1).

%o (PARI) a(n) = sum(k=0, n\4, binomial(n-1, n-4*k)*binomial(4*k, k)/(3*k+1));

%Y Partial sums give A127902.

%Y Cf. A213336, A364410, A366645.

%Y Cf. A002026, A361932.

%K nonn

%O 0,6

%A _Seiichi Manyama_, Oct 15 2023