Shortest (x+1,2x)-code of n.

Terms

a(0) =1a(1) =2a(2) =21a(3) =22a(4) =221a(5) =212a(6) =2121a(7) =222a(8) =2221a(9) =2212a(10) =22121a(11) =2122a(12) =21221a(13) =21212a(14) =212121a(15) =2222a(16) =22221a(17) =22212a(18) =222121a(19) =22122a(20) =221221a(21) =221212a(22) =2212121a(23) =21222a(24) =212221a(25) =212212a(26) =2122121a(27) =212122a(28) =2121221a(29) =2121212