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 A279115 Number of non-equivalent ways to place 6 non-attacking kings on an n X n board. 8
 0, 0, 0, 0, 143, 7855, 153311, 1505465, 9729830, 47235703, 186615092, 630338668, 1882894541, 5092130575, 12686490993, 29498296651, 64664954532, 134715649055, 268438970166, 514318521438, 951646716171, 1706721390223, 2976056379875, 5058962536429, 8402677784738, 13663807273607 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 COMMENTS Rotations and reflections of placements are not counted. If they are to be counted, see A172158. LINKS Heinrich Ludwig, Table of n, a(n) for n = 1..1000 Index entries for linear recurrences with constant coefficients, signature (6,-8,-22,69,-8,-176,168,182,-364,0,364,-182,-168,176,8,-69,22,8,-6,1). FORMULA a(n) = (n^12 - 135*n^10 + 180*n^9 + 7465*n^8 - 18840*n^7 - 202468*n^6 + 749880*n^5 + 2446764*n^4 - 13439400*n^3 - 3570352*n^2 + 89413920*n - 107694720 + IF(MOD(n, 2) = 1, 122*n^6 - 1020*n^5 + 1955*n^4 + 840*n^3 + 5753*n^2 - 42840*n + 132975))/5760 for n>=5. a(n) = 6*a(n-1) - 8*a(n-2) - 22*a(n-3) + 69*a(n-4) - 8*a(n-5) - 176*a(n-6) + 168*a(n-7) + 182*a(n-8) - 364*a(n-9) + 364*a(n-11) - 182*a(n-12) - 168*a(n-13) + 176*a(n-14) + 8*a(n-15) - 69*a(n-16) + 22*a(n-17) + 8*a(n-18) - 6*a(n-19) + a(n-20) for n>=25. G.f.: x^5*(143 +6997*x +107325*x^2 +651585*x^3 +2086471*x^4 +3732434*x^5 +3669293*x^6 +1297859*x^7 -708745*x^8 -592136*x^9 +247421*x^10 +258649*x^11 -53671*x^12 -77714*x^13 +4451*x^14 +14969*x^15 +1018*x^16 -1741*x^17 -234*x^18 +106*x^19) / ((1 -x)^13*(1 +x)^7). - Colin Barker, Dec 09 2016 EXAMPLE There are 143 non-equivalent ways to place 6 non-attacking kings on a 5 X 5 board, e.g., this one: K...K ..... K...K ..... K...K PROG (PARI) concat(vector(4), Vec(x^5*(143 +6997*x +107325*x^2 +651585*x^3 +2086471*x^4 +3732434*x^5 +3669293*x^6 +1297859*x^7 -708745*x^8 -592136*x^9 +247421*x^10 +258649*x^11 -53671*x^12 -77714*x^13 +4451*x^14 +14969*x^15 +1018*x^16 -1741*x^17 -234*x^18 +106*x^19) / ((1 -x)^13*(1 +x)^7) + O(x^30))) \\ Colin Barker, Dec 09 2016 CROSSREFS Cf. A172158, A279111 (2 kings), A279112 (3 kings), A279113 (4 kings), A279114 (5 kings), A279116 (7 kings), A279117, A236679. Sequence in context: A159054 A135946 A217534 * A199039 A199235 A029555 Adjacent sequences: A279112 A279113 A279114 * A279116 A279117 A279118 KEYWORD nonn,easy AUTHOR Heinrich Ludwig, Dec 09 2016 STATUS approved

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Last modified February 26 02:39 EST 2024. Contains 370335 sequences. (Running on oeis4.)