Numbers that have only the digit "1" as first, central and final digit. For numbers with 5 or more digits the rest of digits are "0".
1, 111, 10101, 1001001, 100010001, 10000100001, 1000001000001
1 seqfan posts
Tue Feb 10 17:40:26 CET 2009 [seqfan] A001576