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A004309 Hit polynomials, coefficient of y^2 in N_n(y).
(Formerly M4720)
0
0, 10, 60, 595, 4512, 44802, 457040, 5159517, 62939040, 829049884, 11727029860, 177384144795, 2857827179200, 48865616001564, 883930234491000, 16866107046572417, 338568863790331200, 7132984247370166710, 157374949769998613708 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,2

REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Earl Glen Whitehead, Jr., Four-discordant permutations, J. Austral. Math. Soc. Ser. A 28 (1979), no. 3, 369-377.

LINKS

Table of n, a(n) for n=4..22.

CROSSREFS

Sequence in context: A155633 A002493 A054364 * A281863 A219368 A052664

Adjacent sequences:  A004306 A004307 A004308 * A004310 A004311 A004312

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Sean A. Irvine, Dec 29 2015

STATUS

approved

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Last modified January 17 16:17 EST 2018. Contains 297822 sequences.