Numbers n such that string 3,1 occurs in the base 10 representation of n but not of n-1.

Terms

a(0) =31a(1) =131a(2) =231a(3) =310a(4) =331a(5) =431a(6) =531a(7) =631a(8) =731a(9) =831a(10) =931a(11) =1031a(12) =1131a(13) =1231a(14) =1310a(15) =1331a(16) =1431a(17) =1531a(18) =1631a(19) =1731a(20) =1831a(21) =1931a(22) =2031a(23) =2131a(24) =2231a(25) =2310a(26) =2331a(27) =2431a(28) =2531a(29) =2631