a(n) = 3 + floor((2 + Sum_{j=1..n-1} a(j))/5).

Terms

a(0) =3a(1) =4a(2) =4a(3) =5a(4) =6a(5) =7a(6) =9a(7) =11a(8) =13a(9) =15a(10) =18a(11) =22a(12) =26a(13) =32a(14) =38a(15) =46a(16) =55a(17) =66a(18) =79a(19) =95a(20) =114a(21) =137a(22) =164a(23) =197a(24) =236a(25) =283a(26) =340a(27) =408a(28) =490a(29) =588