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A005974
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Number of unlabeled connected identity interval graphs with n nodes.
(Formerly M3617)
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1
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1, 0, 0, 0, 0, 4, 27, 172, 1141, 8017, 60319, 486372, 4196384, 38621356, 377949874, 3920335179, 42975606304, 496545261764, 6031989895262, 76867521958187, 1025417405366410, 14292224499308110, 207763603833695113, 3144818752057400765
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OFFSET
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1,6
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REFERENCES
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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).
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LINKS
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PROG
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(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
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CROSSREFS
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KEYWORD
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nonn,nice
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AUTHOR
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EXTENSIONS
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a(21) onwards added by N. J. A. Sloane, Oct 19 2006 from the Robinson reference
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STATUS
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approved
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