Numbers with an even number of digits.

Terms

a(0) =10a(1) =11a(2) =12a(3) =13a(4) =14a(5) =15a(6) =16a(7) =17a(8) =18a(9) =19a(10) =20a(11) =21a(12) =22a(13) =23a(14) =24a(15) =25a(16) =26a(17) =27a(18) =28a(19) =29a(20) =30a(21) =31a(22) =32a(23) =33a(24) =34a(25) =35a(26) =36a(27) =37a(28) =38a(29) =39