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 A325447 #23 Feb 16 2025 08:33:58 %S A325447 1,0,3,0,2,8,0,2,6,48,0,2,9,74,383,0,2,10,159,756,6196,0,2,13,276, %T A325447 2058,14634,177083,0,2,14,505,4824,48137,384942,9305118 %N A325447 Triangle read by rows: T(n,k) is the number of simple nonseparable (or 2-connected) graphs on n unlabeled nodes with circumference k, (n >= 3, k >= 3). %H A325447 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/GraphCircumference.html">Graph Circumference</a> %H A325447 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HamiltonianGraph.html">Hamiltonian Graph</a> %F A325447 T(n, 4) = 2 for n > 4. %e A325447 Triangle begins, (n >= 3, k >= 3): %e A325447 1; %e A325447 0, 3; %e A325447 0, 2, 8; %e A325447 0, 2, 6, 48; %e A325447 0, 2, 9, 74, 383; %e A325447 0, 2, 10, 159, 756, 6196; %e A325447 0, 2, 13, 276, 2058, 14634, 177083; %e A325447 0, 2, 14, 505, 4824, 48137, 384942, 9305118; %e A325447 ... %Y A325447 Row sums are A002218(n >= 3). %Y A325447 Right diagonal is A003216. %Y A325447 Cf. A128042, A325455. %K A325447 nonn,tabl,more %O A325447 3,3 %A A325447 _Andrew Howroyd_, Sep 06 2019