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 A122087 Triangle read by rows: T(n,k) = number of unlabeled free bicolored trees with n nodes (n >= 1) and k (1 <= k <= floor(n/2), except k = 0 if n = 1 ) nodes of one color and n-k nodes of the other color (the colors are interchangeable). 1
 1, 1, 1, 1, 1, 1, 2, 1, 2, 3, 1, 3, 7, 1, 3, 10, 9, 1, 4, 14, 28, 1, 4, 19, 45, 37, 1, 5, 24, 73, 132, 1, 5, 30, 105, 242, 168, 1, 6, 37, 152, 412, 693, 1, 6, 44, 204, 660, 1349, 895, 1, 7, 52, 274, 1008, 2472, 3927, 1, 7, 61, 351, 1479, 4219, 8105, 5097, 1, 8 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,7 REFERENCES R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1978. LINKS R. W. Robinson, Rows 1 through 30, flattened EXAMPLE K M N gives the number N of unlabeled free bicolored trees with K nodes of one color and M nodes of the other color. 0 1 1 Total( 1) = 1 1 1 1 Total( 2) = 1 1 2 1 Total( 3) = 1 1 3 1 2 2 1 Total( 4) = 2 1 4 1 2 3 2 Total( 5) = 3 1 5 1 2 4 2 3 3 3 Total( 6) = 6 1 6 1 2 5 3 3 4 7 Total( 7) = 11 1 7 1 2 6 3 3 5 10 4 4 9 Total( 8) = 23 CROSSREFS Row sums give A000055. Sequence in context: A144215 A254539 A283827 * A139642 A264744 A143604 Adjacent sequences:  A122084 A122085 A122086 * A122088 A122089 A122090 KEYWORD nonn,tabf AUTHOR N. J. A. Sloane, Oct 19 2006 STATUS approved

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Last modified May 17 12:01 EDT 2021. Contains 343971 sequences. (Running on oeis4.)