A Connected Graph having Edges is said to be sequential if it is possible to label the nodes with distinct Integers in such that when Edge is labeled , the set of Edge labels is a block of consecutive integers (Grace 1983, Gallian 1990). No Harmonious Graph is known which cannot also be labeled sequentially.

**References**

Gallian, J. A. ``Open Problems in Grid Labeling.'' *Amer. Math. Monthly* **97**, 133-135, 1990.

Grace, T. ``On Sequential Labelings of Graphs.'' *J. Graph Th.* **7**, 195-201, 1983.

© 1996-9

1999-05-26