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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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OFFSET
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0,1
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LINKS
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Table of n, a(n) for n=0..14.
Index entries for linear recurrences with constant coefficients, signature (111,-1110,1000).
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FORMULA
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a(n) = 9*A138148(n) + 6*10^n.
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. A002275 (repunits R_n = (10^n-1)/9), A002283 (9*R_n), A011557 (10^n).
Cf. A138148 (cyclops numbers with binary digits only), A002113 (palindromes).
Cf. A332116 .. A332186 (variants with different repeated digit 1, ..., 8).
Cf. A332190 .. A332197, A181965 (variants with different middle digit 0, ..., 8).
Sequence in context: A266598 A250392 A145250 * A024085 A080474 A079190
Adjacent sequences: A332193 A332194 A332195 * A332197 A332198 A332199
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KEYWORD
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nonn,base,easy
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AUTHOR
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M. F. Hasler, Feb 08 2020
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STATUS
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approved
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