A005219 Number of unlabeled identity unit interval graphs. (Formerly M1289)

0, 0, 0, 0, 0, 2, 4, 15, 36, 108, 276, 771, 2044, 5622, 15204, 41835, 114708, 317382, 879008, 2447951, 6833084, 19146910, 53786076, 151537847, 427946916, 1211440440, 3436543336, 9768382171, 27817787344, 79356481542

Offset

1,6

References

R. W. Robinson, 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

R. W. Robinson, Table of n, a(n) for n = 1..190

Phil Hanlon, Counting interval graphs, Trans. Amer. Math. Soc. 272 (1982), no. 2, 383-426.

Crossrefs

Cf. A007122.

Sequence in context: A073814 A181442 A007122 * A153945 A153942 A055466

Adjacent sequences: A005216 A005217 A005218 * A005220 A005221 A005222

Keyword

nonn,nice

Author

N. J. A. Sloane

Status

approved