I don't think it has been proven to be finite, though it surely is -- there are 5^n n-digit numbers with all digits odd, but the 'chance' that a 3n-digit number has all digits odd is 2^(-3n). (That the last few digits are OK doesn't matter, asymptotically.) The sum of (5/8)^n is of course finite. Charles Greathouse Analyst/Programmer Case Western Reserve University On Wed, Apr 18, 2012 at 11:09 AM, James Buddenhagen <jbuddenh@gmail.com> wrote:
Suppose the positive integers n and n^3 both have all digits odd. Such numbers include 1, 11, 15, 33, 39, 71, 91, 173, 175, 179, 335, 3337, 5597, 7353. Is this list complete? This sequence is http://oeis.org/A085597 in OEIS. But there is no key word indicating that it is a finite sequence. Is this known to be a finite sequence?
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