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Number of unlabeled connected interval graphs with n nodes.
(Formerly M1487)
1

%I M1487 #18 Dec 18 2021 20:39:53

%S 1,1,2,5,15,56,250,1328,8069,54962,410330,3317302,28774874,266242936,

%T 2616100423,27205605275,298569256590,3449309394415,41854968275924,

%U 532353636671777,7083840662453415,98443312509634266,1426382369328881332

%N Number of unlabeled connected interval graphs with n nodes.

%D P. J. Hanlon, personal communication.

%D R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1980.

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H R. W. Robinson, <a href="/A005976/b005976.txt">Table of n, a(n) for n = 1..30</a>

%H Phil Hanlon, <a href="http://dx.doi.org/10.1090/S0002-9947-1982-0662044-8">Counting interval graphs</a>, Trans. Amer. Math. Soc. 272 (1982), no. 2, 383-426.

%K nonn,nice

%O 1,3

%A _N. J. A. Sloane_

%E a(21) onwards added by _N. J. A. Sloane_, Oct 19 2006 from the Robinson reference