Numbers which can be expressed as the product of numbers made of only fours.

Terms

a(0) =1a(1) =4a(2) =16a(3) =44a(4) =64a(5) =176a(6) =256a(7) =444a(8) =704a(9) =1024a(10) =1776a(11) =1936a(12) =2816a(13) =4096a(14) =4444a(15) =7104a(16) =7744a(17) =11264a(18) =16384a(19) =17776a(20) =19536a(21) =28416a(22) =30976a(23) =44444a(24) =45056a(25) =65536a(26) =71104a(27) =78144a(28) =85184a(29) =113664