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 A329789 #11 Dec 02 2019 03:13:30
%S A329789 0,0,2,12,68,400,2496,17338,127660,1030524,8852398,82121018,806839236,
%T A329789 8481362264,93933923996,1104325114202
%N A329789 Total number of graceful labelings of connected graphs with n vertices and n edges.
%C A329789 In general, consider a connected graph with E edges and V vertices. The vertices are given labels in the range 0 to E so that the differences between edges' endpoints are {1,...,E}. None of the vertices are isolated; hence each vertex label participates in at least one edge. For this sequence E = V = n.
%H A329789 D. E. Knuth, <a href="https://cs.stanford.edu/~knuth/programs/graceful-count.w">Program for counting graceful graph labelings.</a>
%Y A329789 Cf. A033472 (V=E+1), A329788 (any V). A diagonal of the triangle in A329790.
%K A329789 nonn,more
%O A329789 1,3
%A A329789 _N. J. A. Sloane_, Dec 01 2019, based on email from _Don Knuth_, Dec 01 2019