a(n) = (7*n + 1)^5.

Terms

a(0) =1a(1) =32768a(2) =759375a(3) =5153632a(4) =20511149a(5) =60466176a(6) =147008443a(7) =312500000a(8) =601692057a(9) =1073741824a(10) =1804229351a(11) =2887174368a(12) =4437053125a(13) =6590815232a(14) =9509900499a(15) =13382255776a(16) =18424351793a(17) =24883200000