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

Terms

a(0) =1a(1) =2a(2) =36a(3) =150a(4) =576a(5) =862a(6) =1492a(7) =1810a(8) =2712a(9) =4210a(10) =4512a(11) =6688a(12) =8110a(13) =8572a(14) =9828a(15) =12496a(16) =14778a(17) =15496a(18) =18222a(19) =20856a(20) =21490a(21) =24420a(22) =26416a(23) =29670a(24) =33460a(25) =36832a(26) =38046a(27) =40086a(28) =41452a(29) =43206