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A091693
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a(n) = (n*10^n - n + 9)/9.
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0
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1, 2, 23, 334, 4445, 55556, 666667, 7777778, 88888889, 1000000000, 11111111111, 122222222222, 1333333333333, 14444444444444, 155555555555555, 1666666666666666, 17777777777777777, 188888888888888888
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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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G.f.: ( 1-20*x+120*x^2-110*x^3 ) / ( (10*x-1)^2*(x-1)^2 ). - R. J. Mathar, Feb 14 2015
a(n) = 22*a(n-1) - 141*a(n-2) + 220*a(n-3) - 100*a(n-4). - Wesley Ivan Hurt, May 17 2023
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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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