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A226320
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a(n) is the smallest k > 6 such that k is a Niven number at least in all the bases from 1 to n.
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4
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7, 8, 8, 8, 8, 12, 12, 24, 24, 24, 24, 24, 24, 432, 720, 720, 720, 720, 720, 840, 840, 840, 3360, 13860, 13860, 13860, 13860, 13860, 40320, 100800, 100800, 2106720, 7698600, 9028800, 9028800, 9028800, 9028800, 9028800, 9028800, 9028800, 9028800, 9028800
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OFFSET
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1,1
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COMMENTS
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The bound a(i) > 6 is motivated by the fact that 1, 2, 4 and 6 are Niven numbers in every base.
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LINKS
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EXAMPLE
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a(8) = 24 because 24 is the smallest k > 6 which is Niven in bases 1 (trivial), 2,..., 8. For example, 24 = (33)_7 = (44)_5 = (220)_3.
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MATHEMATICA
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a[n_] := Block[{k=7}, n > 1 && While[ Max@ Mod[k, Total /@ IntegerDigits[k, Range[2, n]]] > 0, k++]; k]; Array[a, 20]
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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