Every run of digits of n in base 10 has length 2.

Terms

a(0) =11a(1) =22a(2) =33a(3) =44a(4) =55a(5) =66a(6) =77a(7) =88a(8) =99a(9) =1100a(10) =1122a(11) =1133a(12) =1144a(13) =1155a(14) =1166a(15) =1177a(16) =1188a(17) =1199a(18) =2200a(19) =2211a(20) =2233a(21) =2244a(22) =2255a(23) =2266a(24) =2277a(25) =2288a(26) =2299a(27) =3300a(28) =3311a(29) =3322