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Smallest number m such that u + (sum of base-5 digits of u) = m has exactly n solutions.
10

%I #45 Sep 09 2024 15:11:45

%S 0,6,26,632,1953134,30517578152

%N Smallest number m such that u + (sum of base-5 digits of u) = m has exactly n solutions.

%C Indices of records in A230866: a(n) is the index of the first n in A230866.

%C The next two terms are a(7) = 5^165 + 27, a(8) = 5^317 + 633.

%H Pontus von Brömssen, <a href="/A230867/b230867.txt">Table of n, a(n) for n = 1..8</a> (based on comment about a(7) and a(8))

%H Max Alekseyev, <a href="/A230867/a230867.txt">Table of expressions for a(n), for n=1..100</a>

%H Max A. Alekseyev and N. J. A. Sloane, <a href="https://arxiv.org/abs/2112.14365">On Kaprekar's Junction Numbers</a>, arXiv:2112.14365, 2021; Journal of Combinatorics and Number Theory 12:3 (2022), 115-155.

%e a(5) = 1953134 corresponds to the five solutions:

%e 1953099 (base-5: 444444344)

%e 1953103 (base-5: 444444403)

%e 1953105 (base-5: 444444410)

%e 1953129 (base-5: 1000000004)

%e 1953131 (base-5: 1000000011).

%Y A230868 gives the leading power of 5 in a(n).

%Y Smallest number m such that u + (sum of base-b digits of u) = m has exactly n solutions, for bases 2 through 10: A230303, A230640, A230638, A230867, A238840, A238841, A238842, A238843, A006064.

%Y Cf. A230865, A230866.

%K nonn,base

%O 1,2

%A _N. J. A. Sloane_, Nov 05 2013

%E a(5) corrected by _Donovan Johnson_, Nov 05 2013