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A332187
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a(n) = 8*(10^(2n+1)-1)/9 - 10^n.
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3
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7, 878, 88788, 8887888, 888878888, 88888788888, 8888887888888, 888888878888888, 88888888788888888, 8888888887888888888, 888888888878888888888, 88888888888788888888888, 8888888888887888888888888, 888888888888878888888888888, 88888888888888788888888888888, 8888888888888887888888888888888
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,1
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LINKS
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FORMULA
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G.f.: (7 + 101*x - 900*x^2)/((1 - x)(1 - 10*x)(1 - 100*x)).
a(n) = 111*a(n-1) - 1110*a(n-2) + 1000*a(n-3) for n > 2.
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MAPLE
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A332187 := n -> 8*(10^(2*n+1)-1)/9-10^n;
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MATHEMATICA
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Array[8 (10^(2 # + 1)-1)/9 - 10^# &, 15, 0]
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PROG
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(PARI) apply( {A332187(n)=10^(n*2+1)\9*8-10^n}, [0..15])
(Python) def A332187(n): return 10**(n*2+1)//9*8-10**n
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CROSSREFS
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Cf. A138148 (cyclops numbers with binary digits only), A002113 (palindromes).
Cf. A332117 .. A332197 (variants with different "wing" digit 1, ..., 9).
Cf. A332180 .. A332189 (variants with different middle digit 0, ..., 9).
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KEYWORD
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nonn,base,easy
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AUTHOR
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STATUS
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approved
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