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A172137 Number of ways to place 2 nonattacking zebras on an n X n board 7
0, 6, 36, 112, 276, 582, 1096, 1896, 3072, 4726, 6972, 9936, 13756, 18582, 24576, 31912, 40776, 51366, 63892, 78576, 95652, 115366, 137976, 163752, 192976, 225942, 262956, 304336, 350412, 401526, 458032, 520296, 588696, 663622 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Zebra is a (fairy chess) leaper [2,3]

REFERENCES

Christian Poisson, Echecs et mathematiques, Rex Multiplex 29/1990, p.829

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

V. Kotesovec, Number of ways of placing non-attacking queens and kings on boards of various sizes

FORMULA

a(n) = (n^4 - 9n^2 + 40n - 48)/2, n >= 2. (Christian Poisson, 1990)

G.f.: 2*x^2*(4*x^4-8*x^3+4*x^2-3*x-3)/(x-1)^5 [Vaclav Kotesovec, Mar 25 2010]

MATHEMATICA

CoefficientList[Series[2 x (4 x^4 - 8 x^3 + 4 x^2 -3 x - 3) / (x - 1)^5, {x, 0, 40}], x] (* Vincenzo Librandi, May 26 2013 *)

CROSSREFS

Cf. A036464, A172123, A172132.

Sequence in context: A207443 A207437 A199243 * A061804 A207421 A207427

Adjacent sequences:  A172134 A172135 A172136 * A172138 A172139 A172140

KEYWORD

easy,nonn

AUTHOR

Vaclav Kotesovec, Jan 26 2010

STATUS

approved

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Last modified December 18 20:06 EST 2018. Contains 318245 sequences. (Running on oeis4.)