Integer part of n#/((p-3)# 3#), where p=preceding prime to n.

Terms

a(0) =0a(1) =2a(2) =5a(3) =1a(4) =23a(5) =2a(6) =53a(7) =3a(8) =4a(9) =149a(10) =6a(11) =6a(12) =293a(13) =7a(14) =8a(15) =9a(16) =599a(17) =11a(18) =11a(19) =863a(20) =13a(21) =13a(22) =14a(23) =16a(24) =16a(25) =1733a(26) =17a(27) =1943a(28) =18a(29) =21