a(n) = (10*n + 5)^4.

Terms

a(0) =625a(1) =50625a(2) =390625a(3) =1500625a(4) =4100625a(5) =9150625a(6) =17850625a(7) =31640625a(8) =52200625a(9) =81450625a(10) =121550625a(11) =174900625a(12) =244140625a(13) =332150625a(14) =442050625a(15) =577200625a(16) =741200625a(17) =937890625a(18) =1171350625a(19) =1445900625a(20) =1766100625a(21) =2136750625a(22) =2562890625a(23) =3049800625a(24) =3603000625