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A002281
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a(n) = 7*(10^n - 1)/9.
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36
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0, 7, 77, 777, 7777, 77777, 777777, 7777777, 77777777, 777777777, 7777777777, 77777777777, 777777777777, 7777777777777, 77777777777777, 777777777777777, 7777777777777777, 77777777777777777, 777777777777777777, 7777777777777777777, 77777777777777777777, 777777777777777777777
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listen;
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = a(n-1)+7*10^(n-1) with n>0, a(0)=0.
a(n) = 11*a(n-1)-10*a(n-2) with n>1, a(0)=0, a(1)=7. (End)
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MAPLE
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MATHEMATICA
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PROG
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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