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A038720 Next-to-last diagonal of A038719. 3
2, 5, 18, 84, 480, 3240, 25200, 221760, 2177280, 23587200, 279417600, 3592512000, 49816166400, 741015475200, 11769069312000, 198766503936000, 3556874280960000, 67224923910144000, 1338096104497152000 (list; graph; refs; listen; history; internal format)
OFFSET

1,1

REFERENCES

R. B. Nelsen and H. Schmidt, Jr., Chains in power sets, Math. Mag., 64 (1991), 23-31.

LINKS

Index entries for sequences related to posets

FORMULA

(n+3)*n!/2. Half A052572.

CROSSREFS

Cf. A038721.

Sequence in context: A192637 A111916 A118187 * A157312 A175847 A089412

Adjacent sequences:  A038717 A038718 A038719 * A038721 A038722 A038723

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com), May 02 2000

EXTENSIONS

Corrected and extended by Larry Reeves (larryr(AT)acm.org), May 09 2000.

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Last modified February 17 08:34 EST 2012. Contains 205998 sequences.