A005216 Number of unlabeled identity interval graphs with n nodes. (Formerly M3636)

1, 0, 0, 0, 0, 4, 31, 199, 1313, 9158, 68336, 546697, 4682870, 42818887, 416581477, 4298371842, 46896673051, 539527125454, 6528590200432, 82900013695783, 1102289694637302, 15317689255215159, 222056321177147564, 3352587738814695770

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

R. W. Robinson, Table of n, a(n) for n = 1..30

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

Crossrefs

Sequence in context: A270669 A298996 A299663 * A124033 A014537 A136284

Adjacent sequences: A005213 A005214 A005215 * A005217 A005218 A005219

Keyword

nonn

Author

N. J. A. Sloane

Extensions

a(21) onward added by N. J. A. Sloane, Oct 19 2006 from the Robinson reference

Status

approved