The sandpile groups of graphs of classes CH_n (a_1, ..., a_n)

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 CH_n(a_1,…,a_n) is defined. Recurrent and non-recurrent formulas for calculating the sandpile groups of all graphs of classes CH_n (a_1, …, a_n) are proposed.