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A332195
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a(n) = 10^(2n+1) - 4*10^n - 1.
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7
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5, 959, 99599, 9995999, 999959999, 99999599999, 9999995999999, 999999959999999, 99999999599999999, 9999999995999999999, 999999999959999999999, 99999999999599999999999, 9999999999995999999999999, 999999999999959999999999999, 99999999999999599999999999999, 9999999999999995999999999999999
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OFFSET
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0,1
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COMMENTS
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See A183186 = {88, 112, 198, 622, 4228, ...} for the indices of primes.
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LINKS
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FORMULA
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G.f.: (5 + 404*x - 1300*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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A332195 := n -> 10^(n*2+1)-4*10^n-1;
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MATHEMATICA
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Array[ 10^(2 # + 1) - 1 - 4*10^# &, 15, 0]
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PROG
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(PARI) apply( {A332195(n)=10^(n*2+1)-1-4*10^n}, [0..15])
(Python) def A332195(n): return 10**(n*2+1)-1-4*10^n
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CROSSREFS
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Cf. A138148 (cyclops numbers with binary digits only), A002113 (palindromes).
Cf. A332115 .. A332185 (variants with different repeated digit 1, ..., 8).
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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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