PS Perhaps we might call Leroy's sequence the "rigid numbers", on account of their having a "rigid digit"? Jeremy On 16/3/10 19:58, "Leroy Quet" <q1qq2qqq3qqqq at yahoo.com> wrote: > %N A175262 "Obscene numbers": Those positive integers that when written in > binary contain an odd number of digits, the middle digit being a 1.