Integers written in base "triangle".

Terms

a(0) =0a(1) =1a(2) =2a(3) =21a(4) =22a(5) =32a(6) =321a(7) =322a(8) =332a(9) =432a(10) =4321a(11) =4322a(12) =4332a(13) =4432a(14) =5432a(15) =54321a(16) =54322a(17) =54332a(18) =54432a(19) =55432a(20) =65432a(21) =654321a(22) =654322a(23) =654332a(24) =654432a(25) =655432a(26) =665432a(27) =765432a(28) =7654321a(29) =7654322