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A005974 Number of unlabeled connected identity interval graphs with n nodes.
(Formerly M3617)
1
1, 0, 0, 0, 0, 4, 27, 172, 1141, 8017, 60319, 486372, 4196384, 38621356, 377949874, 3920335179, 42975606304, 496545261764, 6031989895262, 76867521958187, 1025417405366410, 14292224499308110, 207763603833695113, 3144818752057400765 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,6
REFERENCES
P. J. Hanlon, personal communication.
R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1980.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
Phil Hanlon, Counting interval graphs, Trans. Amer. Math. Soc. 272 (1982), no. 2, 383-426.
PROG
(Sage) def a(n) : return sum(G.is_connected() and G.is_interval() and G.automorphism_group().order()==1 for G in graphs(n)) # Eric M. Schmidt, Mar 25 2015
CROSSREFS
Sequence in context: A306054 A218274 A061693 * A289718 A010910 A078100
KEYWORD
nonn,nice
AUTHOR
EXTENSIONS
a(21) onwards added by N. J. A. Sloane, Oct 19 2006 from the Robinson reference
Definition edited by Eric M. Schmidt, Mar 25 2015
STATUS
approved

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Last modified March 29 06:57 EDT 2024. Contains 371265 sequences. (Running on oeis4.)