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%I A332181 #8 Feb 11 2020 08:28:24
%S A332181 1,818,88188,8881888,888818888,88888188888,8888881888888,
%T A332181 888888818888888,88888888188888888,8888888881888888888,
%U A332181 888888888818888888888,88888888888188888888888,8888888888881888888888888,888888888888818888888888888,88888888888888188888888888888,8888888888888881888888888888888
%N A332181 a(n) = 8*(10^(2n+1)-1)/9 - 7*10^n.
%H A332181 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (111,-1110,1000).
%F A332181 a(n) = 8*A138148(n) + 10^n = A002282(2n+1) - 7*10^n.
%F A332181 G.f.: (1 + 707*x - 1500*x^2)/((1 - x)(1 - 10*x)(1 - 100*x)).
%F A332181 a(n) = 111*a(n-1) - 1110*a(n-2) + 1000*a(n-3) for n > 2.
%p A332181 A332181 := n -> 8*(10^(2*n+1)-1)/9-7*10^n;
%t A332181 Array[8 (10^(2 # + 1)-1)/9 - 7*10^# &, 15, 0]
%o A332181 (PARI) apply( {A332181(n)=10^(n*2+1)\9*8-7*10^n}, [0..15])
%o A332181 (Python) def A332181(n): return 10**(n*2+1)//9*8-7*10**n
%Y A332181 Cf. (A077776-1)/2 = A183184: indices of primes.
%Y A332181 Cf. A002275 (repunits R_n = (10^n-1)/9), A002282 (8*R_n), A011557 (10^n).
%Y A332181 Cf. A138148 (cyclops numbers with binary digits only).
%Y A332181 Cf. A332121 .. A332191 (variants with different repeated digit 2, ..., 9).
%Y A332181 Cf. A332180 .. A332189 (variants with different middle digit 0, ..., 9).
%K A332181 nonn,base,easy
%O A332181 0,2
%A A332181 _M. F. Hasler_, Feb 08 2020

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