a(n+1) = Sum_{k = 0..floor(2*n/3)} a(k)*a(n-k) for n >= 0 with a(0) = 1.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =4a(5) =7a(6) =15a(7) =34a(8) =72a(9) =165a(10) =387a(11) =861a(12) =2039a(13) =4894a(14) =11256a(15) =27085a(16) =66021a(17) =156347a(18) =381720a(19) =940211a(20) =2261208a(21) =5578659a(22) =13846756a(23) =33654950a(24) =83539418a(25) =208608556a(26) =512069441a(27) =1278522424a(28) =3207377196a(29) =7925966000