a(n) = (8*n+3)^5.

Terms

a(0) =243a(1) =161051a(2) =2476099a(3) =14348907a(4) =52521875a(5) =147008443a(6) =345025251a(7) =714924299a(8) =1350125107a(9) =2373046875a(10) =3939040643a(11) =6240321451a(12) =9509900499a(13) =14025517307a(14) =20113571875a(15) =28153056843a(16) =38579489651a(17) =51888844699a(18) =68641485507a(19) =89466096875