a(n) = (2*n+1)^6.

Terms

a(0) =1a(1) =729a(2) =15625a(3) =117649a(4) =531441a(5) =1771561a(6) =4826809a(7) =11390625a(8) =24137569a(9) =47045881a(10) =85766121a(11) =148035889a(12) =244140625a(13) =387420489a(14) =594823321a(15) =887503681a(16) =1291467969a(17) =1838265625a(18) =2565726409a(19) =3518743761a(20) =4750104241a(21) =6321363049a(22) =8303765625a(23) =10779215329a(24) =13841287201a(25) =17596287801