Write n in ternary then sort the digits.

Terms

a(0) =0a(1) =1a(2) =2a(3) =1a(4) =11a(5) =12a(6) =2a(7) =12a(8) =22a(9) =1a(10) =11a(11) =12a(12) =11a(13) =111a(14) =112a(15) =12a(16) =112a(17) =122a(18) =2a(19) =12a(20) =22a(21) =12a(22) =112a(23) =122a(24) =22a(25) =122a(26) =222a(27) =1a(28) =11a(29) =12