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A284672
Exponents of powers of 7 that contain all ten decimal digits.
2
18, 27, 34, 36, 37, 38, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100
OFFSET
1,1
COMMENTS
It is conjectured that a(n) = n + 34 for n > 27.
LINKS
FORMULA
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
EXAMPLE
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.
CROSSREFS
Cf. A130694 (k=2), A236673 (k=3), A284670 (k=5), this sequence (k=7).
Sequence in context: A226971 A281918 A186129 * A265738 A151741 A090064
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Apr 01 2017
STATUS
approved