Frank Harary and Allen J. Schwenk [The number of caterpillars, Discrete Mathematics, 6 (1973), 359-365] have given an elegant formula for counting the number of non-isomorphic caterpillars on n vertices with n ≥ 3. In this paper we provide an alternate simple proof for Frank Harary and Allen J. Schwenk formula using combination with repetition.

Topics
Bioacoustics of insects
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