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A332126
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a(n) = 2*(10^(2n+1)-1)/9 + 4*10^n.
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3
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6, 262, 22622, 2226222, 222262222, 22222622222, 2222226222222, 222222262222222, 22222222622222222, 2222222226222222222, 222222222262222222222, 22222222222622222222222, 2222222222226222222222222, 222222222222262222222222222, 22222222222222622222222222222, 2222222222222226222222222222222
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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 - 404*x + 200*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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A332126 := n -> 2*(10^(2*n+1)-1)/9+4*10^n;
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MATHEMATICA
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Array[2 (10^(2 # + 1)-1)/9 + 4*10^# &, 15, 0]
Table[FromDigits[Join[PadRight[{}, n, 2], {6}, PadRight[{}, n, 2]]], {n, 0, 20}] (* or *) LinearRecurrence[{111, -1110, 1000}, {6, 262, 22622}, 20] (* Harvey P. Dale, Oct 17 2021 *)
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PROG
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(PARI) apply( {A332126(n)=10^(n*2+1)\9*2+4*10^n}, [0..15])
(Python) def A332126(n): return 10**(n*2+1)//9*2+4*10**n
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CROSSREFS
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Cf. A138148 (cyclops numbers with binary digits), A002113 (palindromes).
Cf. A332116 .. A332196 (variants with different repeated digit 1, ..., 9).
Cf. A332120 .. A332129 (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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