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 A327266 #35 Sep 21 2019 14:38:07
%S A327266 18,2268,22316868,2222332266866868,22222222333322316666886866866868,
%T A327266 2222222222222222333333332222332266666666888866866666886866866868
%N A327266 Product of A325907(n) and its 9's complement.
%F A327266 a(n) = A084021(A325907(n)) = A325907(n) * (A002283(2^(n-1)) - A325907(n)).
%F A327266 a(n) = A327294(n) - 10^(2^(n-1)) = a(n) = (2 * 10^(2^n) - 3 * 10^(2^(n-1)) - 8)/9 - 2 * A325493(n-1) + A325910(n-1) * 10^(2^(n-1)).
%e A327266 a(1) = 3 * 6 = 18.
%e A327266 a(2) = 63 * 36 = 2268.
%e A327266 a(3) = 3363 * 6636 = 22316868.
%e A327266 a(4) = 66663363 * 33336636 = 2222332266866868.
%e A327266 -----------------------------------------------
%e A327266 a(1) = 18 = 18 - 2 * 0 + 0 * 10^1.
%e A327266 a(2) = 2268 = 2188 - 2 * 10 + 1 * 10^2.
%e A327266 a(3) = 22316868 = 22218888 - 2 * 1010 + 10 * 10^4.
%e A327266 a(4) = 2222332266866868 = 2222222188888888 - 2 * 11011010 + 1101 * 10^8.
%o A327266 (Ruby)
%o A327266 def A(n)
%o A327266 a = [3, 6]
%o A327266 b = ([[3]] + (1..n - 1).map{|i| [a[i % 2]] * (2 ** (i - 1))}).reverse.join.to_i
%o A327266 b * (10 ** (2 ** (n - 1)) - 1 - b)
%o A327266 end
%o A327266 def A327266(n)
%o A327266 (1..n).map{|i| A(i)}
%o A327266 end
%o A327266 p A327266(6)
%Y A327266 Cf. A002283, A084021, A178630, A325907, A325910, A325493, A327294.
%K A327266 nonn
%O A327266 1,1
%A A327266 _Seiichi Manyama_, Sep 15 2019