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All positive integers are happy numbers in base 2 and base 4; they are called "happy bases". There are no other happy bases < 500,000,000.
Table of n, a(n) for n=2..100.
Cf. A031177 (Unhappy numbers in base 10)
Sequence in context: A044948 A044949 A044950 * A036461 A244478 A261153
Adjacent sequences: A161869 A161870 A161871 * A161873 A161874 A161875
Jud McCranie, Jun 20 2009