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A172202 Number of ways to place 3 nonattacking kings on a 3 X n board. 7
0, 0, 8, 34, 105, 248, 490, 858, 1379, 2080, 2988, 4130, 5533, 7224, 9230, 11578, 14295, 17408, 20944, 24930, 29393, 34360, 39858, 45914, 52555, 59808, 67700, 76258, 85509, 95480, 106198, 117690, 129983, 143104, 157080, 171938, 187705 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

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-2)*(9n^2-45n+70)/2, n>=2.

G.f.: x^3*(17*x^2+2*x+8)/(x-1)^4. - Vaclav Kotesovec, Mar 24 2010

MATHEMATICA

CoefficientList[Series[x^2 (17 x^2 + 2 x + 8) / (x - 1)^4, {x, 0, 50}], x] (* Vincenzo Librandi, May 27 2013 *)

CROSSREFS

Cf. A061996, A061989, A047659.

Sequence in context: A240785 A066804 A033455 * A053298 A196311 A196284

Adjacent sequences:  A172199 A172200 A172201 * A172203 A172204 A172205

KEYWORD

nonn,easy

AUTHOR

Vaclav Kotesovec, Jan 29 2010

EXTENSIONS

More terms from Vincenzo Librandi, May 27 2013

STATUS

approved

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Last modified December 18 21:01 EST 2018. Contains 318245 sequences. (Running on oeis4.)