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A006787
Number of n-node graphs with no cycles of length less than 5.
(Formerly M0792)
9
1, 2, 3, 6, 11, 23, 48, 114, 293, 869, 2963, 12066, 58933, 347498, 2455693, 20592932, 202724920, 2322206466, 30743624324, 468026657815, 8161170076257
(list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Includes graphs with no cycles at all as well as graphs with girth greater than 5.
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
Table of n, a(n) for n=1..21.
CombOS - Combinatorial Object Server, Generate graphs
Brendan McKay, Emails to N. J. A. Sloane, 1991
Brendan D. McKay, Isomorph-free exhaustive generation, Table 2.
Brendan D. McKay, Isomorph-Free Exhaustive Generation, J. Algorithms, vol. 26 iss. 2 (1998), 306-324.
FORMULA
a(n) = A000088(n) - A128236(n) - A128237(n). - Andrew Howroyd, May 06 2021
CROSSREFS
Cf. A000066, A000088, A054760, A159847, A126757 (connected, inv. Eul. Transf.), A128236, A128237, A300705.
Sequence in context: A123465 A000055 A217312 * A176425 A000992 A036648
Adjacent sequences: A006784 A006785 A006786 * A006788 A006789 A006790
KEYWORD
nonn,more
AUTHOR
N. J. A. Sloane
EXTENSIONS
Definition corrected by Brendan McKay, Apr 27 2007
a(18)-a(19) (from the McKay reference) added by R. J. Mathar, Jun 17 2008
a(20)-a(21) from Brendan McKay, Mar 11 2018
STATUS
approved

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Last modified November 16 07:39 EST 2024. Contains 377784 sequences.
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