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 A379431 #8 Jan 14 2025 17:15:45 %S A379431 1,1,1,1,2,1,2,5,5,2,3,12,17,12,3,6,28,58,58,28,6,10,68,179,247,179, %T A379431 68,10,20,157,538,942,942,538,157,20,35,372,1531,3388,4345,3388,1531, %U A379431 372,35,70,845,4288,11424,18316,18316,11424,4288,845,70 %N A379431 Array read by antidiagonals: A(n,k) is the number of achiral planar maps with n vertices and k faces, n >= 1, k >= 1. %C A379431 The planar maps considered are connected and may contain loops and parallel edges. %C A379431 The number of edges is n + k - 2. %F A379431 A(n,k) = A(k,n). %e A379431 ================================================== %e A379431 n\k | 1 2 3 4 5 6 7 8 ... %e A379431 ----+--------------------------------------------- %e A379431 1 | 1 1 1 2 3 6 10 20 ... %e A379431 2 | 1 2 5 12 28 68 157 372 ... %e A379431 3 | 1 5 17 58 179 538 1531 4288 ... %e A379431 4 | 2 12 58 247 942 3388 11424 ... %e A379431 5 | 3 28 179 942 4345 18316 ... %e A379431 6 | 6 68 538 3388 18316 ... %e A379431 7 | 10 157 1531 11424 ... %e A379431 8 | 20 372 4288 ... %e A379431 ... %e A379431 As a triangle, rows give the number of edges (first row is 0 edges): %e A379431 1; %e A379431 1, 1; %e A379431 1, 2, 1; %e A379431 2, 5, 5, 2; %e A379431 3, 12, 17, 12, 3; %e A379431 6, 28, 58, 58, 28, 6; %e A379431 10, 68, 179, 247, 179, 68, 10; %e A379431 20, 157, 538, 942, 942, 538, 157, 20; %e A379431 35, 372, 1531, 3388, 4345, 3388, 1531, 372, 35; %e A379431 ... %Y A379431 Antidiagonal sums are A006443. %Y A379431 Column 1 is A210736(n-1). %Y A379431 Cf. A269920 (rooted), A277741 (unsensed), A379430 (sensed). %K A379431 nonn,tabl %O A379431 1,5 %A A379431 _Andrew Howroyd_, Jan 14 2025