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Number of unlabeled identity unit interval graphs.
(Formerly M1289)
2

%I M1289 #21 Jan 31 2022 01:32:48

%S 0,0,0,0,0,2,4,15,36,108,276,771,2044,5622,15204,41835,114708,317382,

%T 879008,2447951,6833084,19146910,53786076,151537847,427946916,

%U 1211440440,3436543336,9768382171,27817787344,79356481542

%N Number of unlabeled identity unit interval graphs.

%D R. W. Robinson, 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="/A005219/b005219.txt">Table of n, a(n) for n = 1..190</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.

%Y Cf. A007122.

%K nonn,nice

%O 1,6

%A _N. J. A. Sloane_