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A332142
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a(n) = 4*(10^(2*n+1)-1)/9 - 2*10^n.
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1
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2, 424, 44244, 4442444, 444424444, 44444244444, 4444442444444, 444444424444444, 44444444244444444, 4444444442444444444, 444444444424444444444, 44444444444244444444444, 4444444444442444444444444, 444444444444424444444444444, 44444444444444244444444444444, 4444444444444442444444444444444
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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.: (2 + 202*x - 600*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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A332142 := n -> 4*(10^(2*n+1)-1)/9-2*10^n;
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MATHEMATICA
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Array[4 (10^(2 # + 1)-1)/9 - 2*10^# &, 15, 0]
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PROG
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(PARI) apply( {A332142(n)=10^(n*2+1)\9*4-2*10^n}, [0..15])
(Python) def A332142(n): return 10**(n*2+1)//9*4-2*10**n
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CROSSREFS
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Cf. A138148 (cyclops numbers with binary digits), A002113 (palindromes).
Cf. A332112 .. A332192 (variants with different repeated digit 1, ..., 9).
Cf. A332140 .. A332149 (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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