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 A192202 #7 Oct 21 2019 15:11:27
%S A192202 0,5,9,75,95,99,375,875,975,995,999,6875,9375,9875,9975,9995,9999,
%T A192202 21875,84375,96875,99375,99875,99975,99995,99999,234375,609375,921875,
%U A192202 984375,996875,999375,999875,999975,999995,999999,8046875,9609375,9921875,9984375
%N A192202 Monotonic ordering of nonnegative differences 10^i-5^j, for 40>= i>=0, j>=0.
%t A192202 c = 10; d = 5; t[i_, j_] := c^i - d^j;
%t A192202 u = Table[t[i, j], {i, 0, 40}, {j, 0, i*Log[d, c]}];
%t A192202 v = Union[Flatten[u ]]
%Y A192202 Cf. A192201.
%K A192202 nonn
%O A192202 1,2
%A A192202 _Clark Kimberling_, Jun 25 2011