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A201238
Number of ways to place 4 non-attacking wazirs on an n X n toroidal board.
8
0, 0, 0, 228, 3850, 27225, 122892, 423152, 1213380, 3046025, 6907890, 14454972, 28330822, 52586065, 93218400, 158854080, 261593552, 418045617, 650576150, 988799100, 1471339170, 2147897257, 3081651412, 4352027760, 6057877500, 8321097785, 11290735962
OFFSET
1,4
COMMENTS
Wazir is a leaper [0,1].
FORMULA
a(n) = n^2*(n^2-11)*(n^4 - 19n^2 + 114)/24, n>=5.
G.f.: x^4 * (8x^9 - 54x^8 + 189x^7 - 551x^6 + 1404x^5 - 2552x^4 + 2685x^3 - 783x^2 - 1798x - 228)/(x-1)^9.
MATHEMATICA
CoefficientList[Series[x^3*(8 x^9 - 54 x^8 + 189 x^7 - 551 x^6 + 1404 x^5 - 2552 x^4 + 2685 x^3 - 783 x^2 - 1798 x - 228)/(x - 1)^9, {x, 0, 20}], x] (* Wesley Ivan Hurt, Jan 19 2017 *)
KEYWORD
nonn,easy
AUTHOR
Vaclav Kotesovec, Nov 28 2011
STATUS
approved