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

Terms

a(0) =1a(1) =2a(2) =150a(3) =862a(4) =4210a(5) =6688a(6) =12496a(7) =15496a(8) =24420a(9) =40086a(10) =43206a(11) =67138a(12) =83046a(13) =88426a(14) =102646a(15) =133998a(16) =161092a(17) =169986a(18) =202966a(19) =235288a(20) =243262a(21) =279816a(22) =305068a(23) =346168a(24) =394812a(25) =438568a(26) =454500a(27) =481020a(28) =498936a(29) =521860