The sandpile groups of graphs of classes CHn(a1,..., an).

The article considers the procedure of connection of graphs to the edges of a cyclic graph and its influence on the sandpile group of the graph thus obtained. A series of classes of graphs CHn(a1,..., an) is defined. Re-current and non-recurrent formulas for calculating the sandpile groups of all graphs of classes CHn(a1,..., an) are proposed