Natural numbers written out with their digits grouped in sets of four (leading zeros omitted).

Terms

a(0) =1234a(1) =5678a(2) =9101a(3) =1121a(4) =3141a(5) =5161a(6) =7181a(7) =9202a(8) =1222a(9) =3242a(10) =5262a(11) =7282a(12) =9303a(13) =1323a(14) =3343a(15) =5363a(16) =7383a(17) =9404a(18) =1424a(19) =3444a(20) =5464a(21) =7484a(22) =9505a(23) =1525a(24) =3545a(25) =5565a(26) =7585a(27) =9606a(28) =1626a(29) =3646