A091332 Natural numbers written out with their digits grouped in sets of four (leading zeros omitted).

1234, 5678, 9101, 1121, 3141, 5161, 7181, 9202, 1222, 3242, 5262, 7282, 9303, 1323, 3343, 5363, 7383, 9404, 1424, 3444, 5464, 7484, 9505, 1525, 3545, 5565, 7585, 9606, 1626, 3646, 5666, 7686, 9707, 1727, 3747, 5767, 7787, 9808, 1828, 3848, 5868, 7888