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A055531 Number of labeled order relations on n nodes in which longest chain has 2 nodes. 1
2, 12, 86, 840, 11642, 227892, 6285806, 243593040, 13262556722, 1014466283292, 109128015915206, 16521353903210518, 3524056001906654788, 1059868947134489833998, 449831067019305306983532 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

REFERENCES

L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 60.

LINKS

Table of n, a(n) for n=2..16.

FORMULA

a(n)=A001831(n)-1.

CROSSREFS

A column or diagonal of triangle in A008285. Cf. A052296.

Sequence in context: A179495 A208977 A097237 * A305209 A290568 A181345

Adjacent sequences:  A055528 A055529 A055530 * A055532 A055533 A055534

KEYWORD

easy,nonn

AUTHOR

N. J. A. Sloane, Jul 10 2000

EXTENSIONS

More terms from Vladeta Jovovic, Oct 24 2000

STATUS

approved

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Last modified October 19 17:55 EDT 2018. Contains 316376 sequences. (Running on oeis4.)