Number of terms in n-th derivative of a function composed with itself 4 times.

Terms

a(0) =1a(1) =1a(2) =4a(3) =10a(4) =26a(5) =55a(6) =121a(7) =237a(8) =468a(9) =867a(10) =1597a(11) =2821a(12) =4952a(13) =8421a(14) =14206a(15) =23439a(16) =38324a(17) =61570a(18) =98112a(19) =154111a(20) =240197a(21) =370015a(22) =565802a(23) =856664a(24) =1288366a(25) =1921016a(26) =2846572a(27) =4186730a(28) =6122369a(29) =8893904