Numbers n such that string 2,0 occurs in the base 10 representation of n but not of n-1.

Terms

a(0) =20a(1) =120a(2) =200a(3) =220a(4) =320a(5) =420a(6) =520a(7) =620a(8) =720a(9) =820a(10) =920a(11) =1020a(12) =1120a(13) =1200a(14) =1220a(15) =1320a(16) =1420a(17) =1520a(18) =1620a(19) =1720a(20) =1820a(21) =1920a(22) =2000a(23) =2120a(24) =2200a(25) =2220a(26) =2320a(27) =2420a(28) =2520a(29) =2620