Concatenation of n, n+1 and n.

Terms

a(0) =121a(1) =232a(2) =343a(3) =454a(4) =565a(5) =676a(6) =787a(7) =898a(8) =9109a(9) =101110a(10) =111211a(11) =121312a(12) =131413a(13) =141514a(14) =151615a(15) =161716a(16) =171817a(17) =181918a(18) =192019a(19) =202120a(20) =212221a(21) =222322a(22) =232423a(23) =242524a(24) =252625a(25) =262726a(26) =272827a(27) =282928a(28) =293029a(29) =303130