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%I #9 Mar 08 2019 16:05:17
%S 2,5,2642,546046
%N Untouchable numbers with a record gap to the next untouchable number.
%C The record gap values are 3, 47, 62, 74.
%C Guy asks "How large can the gaps between untouchable numbers be?"
%D Richard K. Guy, Unsolved Problems in Number Theory, 3rd Edition, Springer, 2004, Section B10, p. 101.
%H Giovanni Resta, <a href="http://www.numbersaplenty.com/set/untouchable_number/">Untouchable numbers</a> (terms up to 10^6)
%e 5 is in the sequence since it is an untouchable number and the next untouchable number after it is 52 = 5 + 47 with a record gap of 47. The next gap which is larger than 47 occurs at 2642 which is followed by 2704 = 2642 + 62.
%Y Cf. A005114, A231965.
%K nonn,hard,more
%O 1,1
%A _Amiram Eldar_, Mar 07 2019
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