This site is supported by donations to The OEIS Foundation.

 Annual Appeal: Please make a donation to keep the OEIS running. In 2018 we replaced the server with a faster one, added 20000 new sequences, and reached 7000 citations (often saying "discovered thanks to the OEIS"). Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A061997 Number of ways to place 4 nonattacking kings on an n X n board. 17
 0, 0, 0, 1, 79, 1987, 16834, 85275, 317471, 962089, 2515262, 5882109, 12605095, 25175191, 47443474, 85152487, 146608359, 243516365, 392004286, 613859609, 938008287, 1402264459, 2055382210, 2959442131, 4192607119 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 Vaclav Kotesovec, Number of ways of placing non-attacking queens and kings on boards of various sizes, part of V. Kotesovec, Between chessboard and computer, 1996, pp. 204 - 206. Index entries for linear recurrences with constant coefficients, signature (9,-36,84,-126,126,-84,36,-9,1). FORMULA G.f.: - x^3*(30*x^8 - 361*x^7 + 1186*x^6 - 1060*x^5 - 1209*x^4 + 1711*x^3 + 1312*x^2 + 70*x + 1)/(x - 1)^9. Recurrence: a(n) = 9*a(n - 1) - 36*a(n - 2) + 84*a(n - 3) - 126*a(n - 4) + 126*a(n - 5) - 84*a(n - 6) + 36*a(n - 7) - 9*a(n - 8) + a(n - 9), n >= 12. Explicit formula (K.Fabel and K.Soltsien): a(n) = (n^8 - 54*n^6 + 72*n^5 + 995*n^4 - 2472*n^3 - 5094*n^2 + 21480*n - 17112)/24, n >= 3. a(n) = A193580(n,4). - R. J. Mathar, Sep 03 2016 MATHEMATICA CoefficientList[Series[- x^3 (30 x^8 - 361 x^7 + 1186 x^6 - 1060 x^5 - 1209 x^4 + 1711 x^3 + 1312 x^2 + 70 x + 1) / (x-1)^9, {x, 0, 50}], x] (* Vincenzo Librandi, May 02 2013 *) CROSSREFS Cf. A061995, A061996, A061998. Sequence in context: A194785 A231802 A098104 * A094731 A182347 A293919 Adjacent sequences:  A061994 A061995 A061996 * A061998 A061999 A062000 KEYWORD nonn,easy AUTHOR Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), May 31 2001 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

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