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 A007141 E-trees with at most 2 colors. (Formerly M1757) 3
 1, 2, 7, 22, 75, 250, 886, 3150, 11525, 42698, 160636, 610694, 2345584, 9081850, 35422281, 139022744, 548671671, 2176051206, 8668363781, 34667284600, 139140831224, 560271494924, 2262709876353, 9163000968906, 37198940600718, 151364381619042 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES G. Gati, F. Harary and R. W. Robinson, Line colored trees with extendable automorphisms, Acta Math. Scientia, 2 (1982), 105-110. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS G. Gati, F. Harary, R. W. Robinson, Line colored trees with extendable automorphisms, Acta Mathematica Scientia 2.1 (1982), 105-110. (Annotated scanned copy) FORMULA a(n) = E(2, n) where E(c, 1) = 1, E(c, n) = (1/(n-1)) * Sum_{i=1..n-1} ((c+1) * i - n + 1) * S(c, i) * E(c, n-i) and S(c, 0) = 1 and S(c, n) = Sum_{d | n} E(c, d) [From Gati, Harary, Robinson]. - Sean A. Irvine, Oct 29 2017 CROSSREFS Sequence in context: A137398 A151439 A204218 * A278151 A090831 A174403 Adjacent sequences:  A007138 A007139 A007140 * A007142 A007143 A007144 KEYWORD nonn AUTHOR EXTENSIONS More terms from Sean A. Irvine, Oct 29 2017 STATUS approved

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Last modified June 7 05:20 EDT 2020. Contains 334837 sequences. (Running on oeis4.)