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A257288
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a(n) = 7*8^n-6*7^n.
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5
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1, 14, 154, 1526, 14266, 128534, 1129114, 9738806, 82851706, 697402454, 5821341274, 48265581686, 397988613946, 3266956634774, 26716987140634, 217805235562166, 1770927253556986, 14366815611873494, 116330307978911194, 940412945418752246, 7591696934462256826
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OFFSET
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0,2
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COMMENTS
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First differences of 8^n-7^n = A016177.
a(n-1) is the number of numbers with n digits having the largest digit equal to 7. Note that this is independent of the base b > 7.
Equivalently, number of n-letter words over a 8-letter alphabet, which must not start with the last letter of the alphabet, and in which the first letter of the alphabet must appear.
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LINKS
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FORMULA
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MATHEMATICA
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PROG
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(PARI) a(n)=7*8^n-6*7^n
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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