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URL: https://oeis.org/A303742

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A303742
Number of unlabeled oriented edge-rooted 2-trees which have n triangles.
2
1, 1, 1, 2, 7, 18, 68, 251, 1020, 4258, 18580, 82716, 377207, 1748250, 8227066, 39197164, 188824506, 918333933, 4504366940, 22260929867, 110763984273, 554510459987, 2791460440109, 14123739733754, 71792405634223, 366483503897357, 1878163540497162, 9660232634407657
OFFSET
0,4
LINKS
T. Fowler, I. Gessel, G. Labelle, P. Leroux, The specification of 2-trees, Adv. Appl. Math. 28 (2) (2002) 145-168, Table 1.
PROG
(PARI) C(30, 3) \\ See A340812 for C(n, k). - Andrew Howroyd, May 09 2021
CROSSREFS
Column k=3 of A340812.
Sequence in context: A000988 A185308 A002214 * A340738 A368593 A218684
KEYWORD
nonn
AUTHOR
R. J. Mathar, Apr 29 2018
EXTENSIONS
Name clarified by Andrew Howroyd, May 09 2021
STATUS
approved