a(n) = prime(prime(prime(prime(prime(prime(n)-1)-1)-1)-1)-1)-1, where prime(n) is the n-th prime.

Terms

a(0) =1a(1) =2a(2) =862a(3) =6688a(4) =40086a(5) =67138a(6) =133998a(7) =169986a(8) =279816a(9) =481020a(10) =521860a(11) =843376a(12) =1063156a(13) =1137456a(14) =1337152a(15) =1784610a(16) =2176660a(17) =2307082a(18) =2794248a(19) =3275662a(20) =3395830a(21) =3948472a(22) =4334320a(23) =4964242a(24) =5718550a(25) =6402580a(26) =6652620a(27) =7068780a(28) =7352178a(29) =7715292