a(n) = (5n+1)^6.

Terms

a(0) =1a(1) =46656a(2) =1771561a(3) =16777216a(4) =85766121a(5) =308915776a(6) =887503681a(7) =2176782336a(8) =4750104241a(9) =9474296896a(10) =17596287801a(11) =30840979456a(12) =51520374361a(13) =82653950016a(14) =128100283921a(15) =192699928576a(16) =282429536481