This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A332180 #14 Jul 13 2024 20:26:31
%S A332180 0,808,88088,8880888,888808888,88888088888,8888880888888,
%T A332180 888888808888888,88888888088888888,8888888880888888888,
%U A332180 888888888808888888888,88888888888088888888888,8888888888880888888888888,888888888888808888888888888,88888888888888088888888888888,8888888888888880888888888888888
%N A332180 a(n) = 8*(10^(2n+1)-1)/9 - 8*10^n.
%H A332180 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (111,-1110,1000).
%F A332180 a(n) = 8*A138148(n) = A002282(2n+1) - 8*10^n.
%F A332180 G.f.: 8*x*(101 - 200*x)/((1 - x)(1 - 10*x)(1 - 100*x)).
%F A332180 a(n) = 111*a(n-1) - 1110*a(n-2) + 1000*a(n-3) for n > 2.
%F A332180 E.g.f.: 8*exp(x)*(10*exp(99*x) - 9*exp(9*x) - 1)/9. - _Stefano Spezia_, Jul 13 2024
%p A332180 A332180 := n -> 8*((10^(2*n+1)-1)/9-10^n);
%t A332180 Array[8 ((10^(2 # + 1)-1)/9 - 10^#) &, 15, 0]
%o A332180 (PARI) apply( {A332180(n)=(10^(n*2+1)\9-10^n)*8}, [0..15])
%o A332180 (Python) def A332180(n): return (10**(n*2+1)//9-10**n)*8
%Y A332180 Cf. A002275 (repunits R_n = (10^n-1)/9), A002282 (8*R_n), A011557 (10^n).
%Y A332180 Cf. A138148 (cyclops numbers with binary digits only), A002113 (palindromes).
%Y A332180 Cf. A332120 .. A332190 (variants with different repeated digit 2, ..., 9).
%Y A332180 Cf. A332181 .. A332189 (variants with different middle digit 1, ..., 9).
%Y A332180 Subsequence of A006072 (numbers with mirror symmetry about middle), A153806 (strobogrammatic cyclops numbers), and A204095 (numbers whose decimal digits are in {0,8}).
%K A332180 nonn,base,easy
%O A332180 0,2
%A A332180 _M. F. Hasler_, Feb 08 2020