Converting among Dyadic, Decimal, and Binary Notation
This Demonstration converts among dyadic, decimal, and binary notation for positive integers. Dyadic notation is much like binary, except that it uses 1s and 2s instead of 0s and 1s. The dyadic numeral "1212" stands for "one eight, two fours, one two, and two ones." This adds up to 20 (in decimal notation). In binary notation this is "10100", which stands for one 16 plus one four.
 D. Hofstadter, "How Raymond Smullyan Inspired My 1112-Year-Old Self," Four Lives, A Celebration of Raymond Smullyan (J. Rosenhouse, ed.), New York: Dover Publications, Inc., 2014 pp. 87–104.