a(n) = 625*n^2 - 2*n.

Terms

a(0) =623a(1) =2496a(2) =5619a(3) =9992a(4) =15615a(5) =22488a(6) =30611a(7) =39984a(8) =50607a(9) =62480a(10) =75603a(11) =89976a(12) =105599a(13) =122472a(14) =140595a(15) =159968a(16) =180591a(17) =202464a(18) =225587a(19) =249960a(20) =275583a(21) =302456a(22) =330579a(23) =359952a(24) =390575a(25) =422448a(26) =455571a(27) =489944a(28) =525567a(29) =562440