a(n) = Sum_{k=0..floor(n/3)} binomial(n-2*k,k) * binomial(2*(n-3*k),n-3*k).

A383581

a(n) = Sum_{k=0..floor(n/3)} binomial(n-2*k,k) * binomial(2*(n-3*k),n-3*k).

Terms

    a(0) =1a(1) =2a(2) =6a(3) =21a(4) =74a(5) =270a(6) =1005a(7) =3788a(8) =14418a(9) =55289a(10) =213270a(11) =826614a(12) =3216629a(13) =12558928a(14) =49175136a(15) =193023965a(16) =759299438a(17) =2992534344a(18) =11813985377a(19) =46709675040a(20) =184928644350a(21) =733047010709

External references