

A172964


Number of ways to place 2 nonattacking knights on an n X n cylindrical board.


5



0, 4, 18, 92, 230, 522, 1022, 1808, 2970, 4610, 6842, 9792, 13598, 18410, 24390, 31712, 40562, 51138, 63650, 78320, 95382, 115082, 137678, 163440, 192650, 225602, 262602, 303968, 350030, 401130, 457622, 519872, 588258, 663170, 745010, 834192, 931142, 1036298, 1150110
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OFFSET

1,2


LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000
V. Kotesovec, Number of ways of placing nonattacking queens and kings on boards of various sizes


FORMULA

a(n) = n*(n^3  9*n + 12)/2, n>=5.
G.f.: 2*x^2*(6*x^730*x^6+61*x^566*x^4+45*x^321*x^2+x2)/(x1)^5.  Vaclav Kotesovec, Mar 25 2010


MATHEMATICA

CoefficientList[Series[2 x (6 x^7  30 x^6 + 61 x^5  66 x^4 + 45 * x^3  21 x^2 + x  2) / (x  1)^5, {x, 0, 50}], x] (* Vincenzo Librandi, May 29 2013 *)


CROSSREFS

Cf. A172529, A172132.
Sequence in context: A355247 A269450 A206639 * A317135 A196150 A185298
Adjacent sequences: A172961 A172962 A172963 * A172965 A172966 A172967


KEYWORD

nonn,easy


AUTHOR

Vaclav Kotesovec, Feb 06 2010


EXTENSIONS

More terms from Vincenzo Librandi, May 29 2013


STATUS

approved



