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 A343870 #26 Jul 11 2023 08:57:10 %S A343870 1,0,0,0,1,0,0,0,1,0,0,0,1,1,0,0,0,1,2,1,0,0,0,0,3,3,1,0,0,0,0,2,9,4, %T A343870 1,0,0,0,0,1,13,20,6,1,0,0,0,0,0,11,49,40,7,1,0,0,0,0,0,5,77,158,70,9, %U A343870 1,0,0,0,0,0,2,75,406,426,121,11,1,0,0,0,0,0,0,47,662,1645,1018,189,13,1,0 %N A343870 Triangle read by rows: T(n,k) is the number of unlabeled nonseparable (or 2-connected) planar graphs with n edges and k nodes (n >= 1, 2 <= k <= n + 1). %H A343870 Georg Grasegger, <a href="/A343870/b343870.txt">Table of n, a(n) for n = 1..351 (26 rows)</a> (first 210 terms (20 rows) from Andrew Howroyd) %F A343870 T(n, n) = 1 for n >= 3. %F A343870 T(n, n-1) = A253186(n-3) for n >= 3. %e A343870 Triangle T(n,k) begins (n edges >= 1, k vertices >= 2): %e A343870 1; %e A343870 0, 0; %e A343870 0, 1, 0; %e A343870 0, 0, 1, 0; %e A343870 0, 0, 1, 1, 0; %e A343870 0, 0, 1, 2, 1, 0; %e A343870 0, 0, 0, 3, 3, 1, 0; %e A343870 0, 0, 0, 2, 9, 4, 1, 0; %e A343870 0, 0, 0, 1, 13, 20, 6, 1, 0; %e A343870 0, 0, 0, 0, 11, 49, 40, 7, 1, 0; %e A343870 0, 0, 0, 0, 5, 77, 158, 70, 9, 1, 0; %e A343870 0, 0, 0, 0, 2, 75, 406, 426, 121, 11, 1, 0; %e A343870 ... %o A343870 (nauty) geng -C $k $n:$n | planarg -q | countg -q # _Georg Grasegger_, Jun 05 2023 %Y A343870 Row sums are A343869. %Y A343870 Column sums are A021103. %Y A343870 Cf. A049334, A049336 (transpose), A049337, A253186, A339070. %K A343870 nonn,tabl %O A343870 1,19 %A A343870 _Andrew Howroyd_, May 04 2021