a(n) = (6*n + 3)^5.

Terms

a(0) =243a(1) =59049a(2) =759375a(3) =4084101a(4) =14348907a(5) =39135393a(6) =90224199a(7) =184528125a(8) =345025251a(9) =601692057a(10) =992436543a(11) =1564031349a(12) =2373046875a(13) =3486784401a(14) =4984209207a(15) =6956883693a(16) =9509900499a(17) =12762815625a(18) =16850581551a(19) =21924480357a(20) =28153056843a(21) =35723051649a(22) =44840334375a(23) =55730836701