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%I #20 Apr 07 2020 23:18:24
%S 18,27,34,36,37,38,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,
%T 57,58,59,60,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,
%U 81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100
%N Exponents of powers of 7 that contain all ten decimal digits.
%C It is conjectured that a(n) = n + 34 for n > 27.
%H Seiichi Manyama, <a href="/A284672/b284672.txt">Table of n, a(n) for n = 1..10000</a>
%F G.f.: x*(-x^28 + x^27 - x^7 + x^6 - x^4 - 5*x^3 - 2*x^2 - 9*x + 18)/(x - 1)^2 (as conjectured in comments). - _Chai Wah Wu_, Jan 26 2020
%e 7^18 = 1628413597910449, which contains three 1's, one 2, one 3, three 4's, one 5, one 6, one 7, one 8, three 9's and one 0, so 18 is in the sequence.
%Y Cf. A130694 (k=2), A236673 (k=3), A284670 (k=5), this sequence (k=7).
%K nonn
%O 1,1
%A _Seiichi Manyama_, Apr 01 2017