The numbers 9-44 are represented by 20, 21, 22, 23, 24, 25, 26, 27, 28, 40, 41, 42, 43, 44, 45, 46, 47, 48, 60, 61, 62, 63, 64, 65, 66, 67, 68, 80, 81, 82, 83, 84, 85, 86, 87, 88 respectively in base 9/2. These are the only integers with two digits, and so a(2)=36.