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 A369223 #25 Feb 16 2025 08:34:06
%S A369223 1,1,2,3,6,11,35,134,1183,21319,761871
%N A369223 Number of uniquely colorable simple graphs on n nodes.
%C A369223 The only disconnected uniquely colorable graphs are the empty graphs on n > 1 nodes.
%H A369223 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SimpleGraph.html">Simple Graph</a>.
%H A369223 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/UniquelyColorableGraph.html">Uniquely Colorable Graph</a>.
%F A369223 a(n) = Sum_{k=1..n} A369227(n,k).
%e A369223 n = 1: singleton graph K_1 (1 graph).
%e A369223 n = 2: 2-empty graph, path graph P_2 (2 graphs).
%e A369223 n = 3: 3-empty graph, path graph P_3, triangle graph C_3 = K_3 (3 graphs).
%e A369223 n = 4: 4-empty graph, claw graph K_{1,3}, diamond graph K_{1,1,2} = K_4-e, P_4, square graph C_4, tetrahedral graph K_4 (6 graphs).
%Y A369223 Cf. A001349.
%Y A369223 Cf. A369227 (triangle by chromatic number).
%K A369223 nonn,more
%O A369223 0,3
%A A369223 _Eric W. Weisstein_, Jan 16 2024