Numbers of the form 4^i * 9^j, with i, j >= 0.

Terms

a(0) =1a(1) =4a(2) =9a(3) =16a(4) =36a(5) =64a(6) =81a(7) =144a(8) =256a(9) =324a(10) =576a(11) =729a(12) =1024a(13) =1296a(14) =2304a(15) =2916a(16) =4096a(17) =5184a(18) =6561a(19) =9216a(20) =11664a(21) =16384a(22) =20736a(23) =26244a(24) =36864a(25) =46656a(26) =59049a(27) =65536a(28) =82944a(29) =104976