a(0) = 1; a(n) = Sum_{k=0..floor((n-1)/5)} a(5*k) * a(n-1-5*k).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =2a(7) =3a(8) =4a(9) =5a(10) =6a(11) =13a(12) =21a(13) =30a(14) =40a(15) =51a(16) =114a(17) =190a(18) =280a(19) =385a(20) =506a(21) =1150a(22) =1950a(23) =2925a(24) =4095a(25) =5481a(26) =12586a(27) =21576a(28) =32736a(29) =46376