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 A096203 #16 Nov 08 2019 22:26:59 %S A096203 1,2,3,7,18,66,239,963,3792,15230,60297,240295,952530,3783000, %T A096203 14999274,59492918,235852544,935260075,3707948564,14702345112, %U A096203 58294850481,231152521791,916584704599,3634684693457,14413639272087 %N A096203 Number of coverings of {1..n} by translation and reflection of a single set. %e A096203 a(4) = 7 because the following are the 7 coverings of {1...4}, each one of which only uses a single set and its translations and reflections: %e A096203 {{1}, {2}, {3}, {4}}; %e A096203 {{1, 2}, {3, 4}}; %e A096203 {{1, 2}, {2, 3}, {3, 4}}; %e A096203 {{1, 3}, {2, 4}}; %e A096203 {{1, 2, 4}, {1, 3, 4}}; %e A096203 {{1, 2, 3}, {2, 3, 4}}; %e A096203 {{1, 2, 3, 4}}. %e A096203 . %e A096203 a(5) = 18 because the following are the 18 coverings of {1...5}, each one of which only uses a single set and its translations and reflections: %e A096203 {{1}, {2}, {3}, {4}, {5}}; %e A096203 {{1, 2}, {2, 3}, {3, 4}, {4, 5}}; %e A096203 {{1, 2}, {2, 3}, {4, 5}}; %e A096203 {{1, 2}, {3, 4}, {4, 5}}; %e A096203 {{1, 3}, {2, 4}, {3, 5}}; %e A096203 {{1, 2, 4}, {1, 3, 4}, {2, 3, 5}, {2, 4, 5}}; %e A096203 {{1, 2, 4}, {1, 3, 4}, {2, 3, 5}}; %e A096203 {{1, 2, 4}, {1, 3, 4}, {2, 4, 5}}; %e A096203 {{1, 2, 4}, {2, 3, 5}, {2, 4, 5}}; %e A096203 {{1, 3, 4}, {2, 3, 5}, {2, 4, 5}}; %e A096203 {{1, 2, 3}, {2, 3, 4}, {3, 4, 5}}; %e A096203 {{1, 2, 4}, {2, 3, 5}}; %e A096203 {{1, 3, 4}, {2, 3, 5}}; %e A096203 {{1, 3, 4}, {2, 4, 5}}; %e A096203 {{1, 2, 3}, {3, 4, 5}}; %e A096203 {{1, 2, 3, 5}, {1, 3, 4, 5}}; %e A096203 {{1, 2, 3, 4}, {2, 3, 4, 5}}; %e A096203 {{1, 2, 3, 4, 5}}. %Y A096203 Cf. A096202 (if only translations allowed). %Y A096203 Cf. A096154, A329128. %K A096203 nonn %O A096203 1,2 %A A096203 _Jon Wild_, Jul 27 2004 %E A096203 Corrected by _Andrew Howroyd_, Nov 08 2019