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%I #14 Oct 14 2014 15:34:27
%S 1,3,4,5,7,14,9,11,13,19
%N Least number k > 0 such that k^k contains exactly n distinct digits.
%C Unlike A054039 and A247794, "...at least n..." and "...exactly n..." are two different sequences. a(n) above gives "...exactly n..." whereas, for "...at least n...", the sequence would be 1, 3, 4, 5, 7, 9, 9, 11, 13, 19, where a(6) would be 9 instead of 14.
%e 7^7 = 823543 has 5 distinct digits. 6^6, 5^5, 4^4, 3^3, 2^2, and 1^1 all do not have 5 distinct digits. So a(5) = 7.
%o (PARI)
%o a(n)=k=1; while(#vecsort(digits(k^k), , 8)!=n, k++); k
%o vector(10,n,a(n))
%Y Cf. A000312, A054039, A247794, A239306.
%K nonn,base,fini,full,easy
%O 1,2
%A _Derek Orr_, Sep 30 2014
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