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A241156 Number of complementary pairs of `homogenized' N-free graphs with n nodes. 1
1, 1, 2, 7, 22, 82, 308, 1225, 4954, 20558, 86572, 369942, 1598172, 6972100, 30663656, 135826627, 605386062, 2713066882, 12217967284, 55262144418, 250932354484, 1143468874748, 5227460728344, 23968152050930, 110191808568852, 507857114699628 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..26.

P. J. Cameron, Some treelike objects, Quart. J. Math. Oxford, 38 (1987), 155-183. See p. 166.

Jacinta Covington, A universal structure for N-free graphs, Proc. London Math. Soc. (3) 58 (1989), no. 1, 1--16. MR0969544 (89m:03028).

FORMULA

a(1)=1, thereafter a(n) = A226909(n)/2.

CROSSREFS

Cf. A226909.

Sequence in context: A097967 A052879 A007867 * A014558 A150322 A150323

Adjacent sequences:  A241153 A241154 A241155 * A241157 A241158 A241159

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Apr 18 2014

STATUS

approved

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Last modified October 16 16:08 EDT 2019. Contains 328101 sequences. (Running on oeis4.)