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%I M1757 #19 Oct 30 2017 03:31:05
%S 1,2,7,22,75,250,886,3150,11525,42698,160636,610694,2345584,9081850,
%T 35422281,139022744,548671671,2176051206,8668363781,34667284600,
%U 139140831224,560271494924,2262709876353,9163000968906,37198940600718,151364381619042
%N E-trees with at most 2 colors.
%D G. Gati, F. Harary and R. W. Robinson, Line colored trees with extendable automorphisms, Acta Math. Scientia, 2 (1982), 105-110.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H G. Gati, F. Harary, R. W. Robinson, <a href="/A003238/a003238.pdf">Line colored trees with extendable automorphisms</a>, Acta Mathematica Scientia 2.1 (1982), 105-110. (Annotated scanned copy)
%H <a href="/index/Tra#trees">Index entries for sequences related to trees</a>
%F 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
%K nonn
%O 1,2
%A _N. J. A. Sloane_.
%E More terms from _Sean A. Irvine_, Oct 29 2017
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