a(2) = 1, then (p-1)*(p-4)/2, with p = prime(n), n > 2.

Terms

a(0) =1a(1) =2a(2) =9a(3) =35a(4) =54a(5) =104a(6) =135a(7) =209a(8) =350a(9) =405a(10) =594a(11) =740a(12) =819a(13) =989a(14) =1274a(15) =1595a(16) =1710a(17) =2079a(18) =2345a(19) =2484a(20) =2925a(21) =3239a(22) =3740a(23) =4464a(24) =4850a(25) =5049a(26) =5459a(27) =5670a(28) =6104a(29) =7749