[math-fun] Orphan numbers
Hello Math-Fun, Let's call K the kid of integer J. K is the concatenation of the successive absolute differences of J's digits: For J = 2019, we have K = 218. Note that 22019 has the same "218" kid because we don't accept the possible leading 0s of K. Orphan numbers are integers with no father, like 919 or 68955. Is a list of such orphan numbers already in the OEIS? Not sure... Best, É.
EA: "Orphan numbers are integers with no father, like 919 or [68956]. Is a list of such orphan numbers already in the OEIS?" http://oeis.org/A271639
Eventually almost all numbers are orphans, because there are some impossible substrings, like 919, and any number containing the bad substring is also an orphan. And the fraction of numbers containing any single substring rises asymptotically to 1 (albeit usually slowly). On Thu, Oct 31, 2019 at 2:59 PM Hans Havermann <gladhobo@bell.net> wrote:
EA: "Orphan numbers are integers with no father, like 919 or [68956]. Is a list of such orphan numbers already in the OEIS?"
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participants (3)
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Allan Wechsler -
Hans Havermann -
Éric Angelini