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A332140
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a(n) = 4*(10^(2n+1)-1)/9 - 4*10^n.
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9
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0, 404, 44044, 4440444, 444404444, 44444044444, 4444440444444, 444444404444444, 44444444044444444, 4444444440444444444, 444444444404444444444, 44444444444044444444444, 4444444444440444444444444, 444444444444404444444444444, 44444444444444044444444444444, 4444444444444440444444444444444
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listen;
history;
text;
internal format)
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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.: 4*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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A332140 := n -> 4*((10^(2*n+1)-1)/9-10^n);
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MATHEMATICA
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Array[4 ((10^(2 # + 1)-1)/9 - 10^#) &, 15, 0]
LinearRecurrence[{111, -1110, 1000}, {0, 404, 44044}, 20] (* Harvey P. Dale, Jul 06 2021 *)
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PROG
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(PARI) apply( {A332140(n)=(10^(n*2+1)\9-10^n)*4}, [0..15])
(Python) def A332140(n): return (10**(n*2+1)//9-10**n)*4
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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. A332141 .. A332149 (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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