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A332150
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a(n) = 5*(10^(2n+1)-1)/9 - 5*10^n.
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9
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0, 505, 55055, 5550555, 555505555, 55555055555, 5555550555555, 555555505555555, 55555555055555555, 5555555550555555555, 555555555505555555555, 55555555555055555555555, 5555555555550555555555555, 555555555555505555555555555, 55555555555555055555555555555, 5555555555555550555555555555555
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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.: 5*x*(101 - 200*x)/((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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A332150 := n -> 5*((10^(2*n+1)-1)/9-10^n);
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MATHEMATICA
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Array[5 ((10^(2 # + 1)-1)/9 - 10^#) &, 15, 0]
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PROG
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(PARI) apply( {A332150(n)=(10^(n*2+1)\9-10^n)*5}, [0..15])
(Python) def A332150(n): return (10**(n*2+1)//9-10**n)*5
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CROSSREFS
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Cf. A138148 (cyclops numbers with binary digits), A002113 (palindromes).
Cf. A332120 .. A332190 (variants with different repeated digit 2, ..., 9).
Cf. A332151 .. A332159 (variants with different middle digit 1, ..., 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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