Comtet, L. Advanced Combinatorics: The Art of Finite and Infinite Expansions, rev. enl. ed. Dordrecht,
Netherlands: Reidel, p. 55, 1974.Cyvin, S. J. et al. .
"Enumeration of Constitutional Isomers of Polyenes." J. Molec. Structure
(Theorochem.)357, 255-261, 1995.Etherington, I. M. H.
"Non-Associate Powers and a Functional Equation." Math. Gaz.21,
36-39 and 153, 1937.Etherington, I. M. H. "On Non-Associative
Combinations." Proc. Royal Soc. Edinburgh59, 153-162, 1938-39.Finch,
S. R. "Otter's Tree Enumeration Constants." §5.6 in Mathematical
Constants. Cambridge, England: Cambridge University Press, pp. 295-316,
2003.Franklin, J. N. and Golomb, S. W. "A Function-Theoretic
Approach to the Study of Nonlinear Recurring Sequences." Pacific J. Math.56,
467, 1975.Harary, F. Graph
Theory. Reading, MA: Addison-Wesley, 1969.Harary, F. and Palmer,
E. M. Graphical
Enumeration. New York: Academic Press, 1973.Knuth, D. E.
The
Art of Computer Programming, Vol. 1: Fundamental Algorithms, 3rd ed.
Reading, MA: Addison-Wesley, 1997.Olds, C. D. "Problem 4277:
Genetic Algebra." Amer. Math. Monthly56, 697-699, 1949.Otter,
R. "The Number of Trees." Ann. Math.49, 583-599, 1948.Sloane,
N. J. A. Sequences A001190/M0790
A072191, A086317,
and A086318 in "The On-Line Encyclopedia
of Integer Sequences."Stanley, R. P. Problem 6.52 in Enumerative
Combinatorics, Vol. 2. Cambridge, England: Cambridge University Press,
1999.Wedderburn, J. H. M. "The Functional Equation ." Ann. Math.24,
121-140, 1922-1923.