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A332196
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a(n) = 10^(2n+1) - 1 - 3*10^n.
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7
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6, 969, 99699, 9996999, 999969999, 99999699999, 9999996999999, 999999969999999, 99999999699999999, 9999999996999999999, 999999999969999999999, 99999999999699999999999, 9999999999996999999999999, 999999999999969999999999999, 99999999999999699999999999999
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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.: (6 + 303*x - 1200*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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A332196 := n -> 10^(n*2+1)-1-3*10^n;
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MATHEMATICA
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Array[ 10^(2 # + 1) - 1 - 3*10^# &, 15, 0]
FromDigits/@Table[Join[PadLeft[{6}, n, 9], PadRight[{}, n-1, 9]], {n, 30}] (* or *) LinearRecurrence[{111, -1110, 1000}, {6, 969, 99699}, 30] (* Harvey P. Dale, May 03 2021 *)
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PROG
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(PARI) apply( {A332196(n)=10^(n*2+1)-1-3*10^n}, [0..15])
(Python) def A332196(n): return 10**(n*2+1)-1-3*10^n
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CROSSREFS
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Cf. A138148 (cyclops numbers with binary digits only), A002113 (palindromes).
Cf. A332116 .. A332186 (variants with different repeated digit 1, ..., 8).
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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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