a(n) = (2*n)^7.

Terms

a(0) =0a(1) =128a(2) =16384a(3) =279936a(4) =2097152a(5) =10000000a(6) =35831808a(7) =105413504a(8) =268435456a(9) =612220032a(10) =1280000000a(11) =2494357888a(12) =4586471424a(13) =8031810176a(14) =13492928512a(15) =21870000000a(16) =34359738368a(17) =52523350144a(18) =78364164096a(19) =114415582592a(20) =163840000000a(21) =230539333248a(22) =319277809664a(23) =435817657216