Numbers k such that k-1 | concat(k, k+1).

Terms

a(0) =2a(1) =3a(2) =4a(3) =5a(4) =7a(5) =18a(6) =35a(7) =52a(8) =168a(9) =335a(10) =502a(11) =1668a(12) =3335a(13) =5002a(14) =14287a(15) =16668a(16) =33335a(17) =50002a(18) =166668a(19) =333335a(20) =500002a(21) =1666668a(22) =3333335a(23) =5000002a(24) =16666668a(25) =33333335a(26) =50000002a(27) =166666668a(28) =333333335a(29) =500000002