OFFSET
1,5
COMMENTS
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.
LINKS
D. E. Knuth, Program for counting graceful graph labelings.
D. E. Knuth, Output from program
EXAMPLE
Rows 1 through 16 are:
0,1,
0,0,2,
0,0,2,4,
0,0,0,12,12,
0,0,0,8,68,40,
0,0,0,2,106,400,164,
0,0,0,0,88,1184,2496,752,
0,0,0,0,32,1728,11932,17338,4020,
0,0,0,0,8,1696,29444,121084,127660,23576,
0,0,0,0,0,964,45472,442222,1259838,1030524,155632,
0,0,0,0,0,432,50292,1051048,6488844,13590300,8852398,1112032,
0,0,0,0,0,104,40176,1744982,21410862,93887854,153385084,82121018,8733628,
0,0,0,0,0,24,24688,2250864,51470648,420080516,1378054500,1803091192,806839236,73547332,
0,0,0,0,0,0,11208,2184056,92513144,1340857860,7975757616,20604457050,22263918324,8481362264,670789524,
0,0,0,0,0,0,3780,1818244,136668880,3335302886,33380409234,151167588580,315541333316,286284099998,93933923996,6502948232,
0,0,0,0,0,0,864,1141312,159551124,6537511962,106698003000,795992914532,2869123162654,4974721374674,3859250594040,1104325114202,67540932632,
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
N. J. A. Sloane, Dec 02 2019, based on email from Don Knuth, Dec 01 2019
STATUS
approved