Sums of 3 distinct powers of 4.

Terms

a(0) =21a(1) =69a(2) =81a(3) =84a(4) =261a(5) =273a(6) =276a(7) =321a(8) =324a(9) =336a(10) =1029a(11) =1041a(12) =1044a(13) =1089a(14) =1092a(15) =1104a(16) =1281a(17) =1284a(18) =1296a(19) =1344a(20) =4101a(21) =4113a(22) =4116a(23) =4161a(24) =4164a(25) =4176a(26) =4353a(27) =4356a(28) =4368a(29) =4416