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!)
 A172217 Number of ways to place 7 nonattacking knights on a 7 X n board. 2
 1, 78, 1758, 38588, 383246, 2135344, 8891854, 30108310, 86669806, 219845764, 504261973, 1065642840, 2104251027, 3924818982, 6973786593, 11884673662, 19532410762, 31097451768, 48140491605, 72688612756, 107333684073 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 FORMULA a(n) = (117649n^7-2571471n^6+29223943n^5-216954465n^4+1114503256n^3-3907492824n^2+8562799512n-8962924320)/720,n>=12. For any fixed value of k > 1, a(n) = 1/k!*(kn)^k - 3(k-1)(3k-4)/2/k!*(kn)^(k-1) + ... G.f.: x * (252*x^18 -272*x^17 -5134*x^16 +14468*x^15 +19721*x^14 -132666*x^13 +174233*x^12 +119440*x^11 -540473*x^10 +654954*x^9 -89133*x^8 -93778*x^7 +497782*x^6 +56796*x^5 +119468*x^4 +26652*x^3 +1162*x^2 +70*x +1) / (x-1)^8. - Vaclav Kotesovec, Mar 25 2010 MATHEMATICA CoefficientList[Series[(252 x^18 - 272 x^17 - 5134 x^16 + 14468 x^15 + 19721 x^14 - 132666 x^13 + 174233 x^12 + 119440 x^11 - 540473 x^10 + 654954 x^9 - 89133 x^8 - 93778 x^7 + 497782 x^6 + 56796 x^5 + 119468 x^4 + 26652 x^3 + 1162 x^2 + 70 x + 1) / (x - 1)^8, {x, 0, 50}], x] (* Vincenzo Librandi, May 27 2013 *) CROSSREFS Cf. A061993, A172212, A172213, A172214, A172215. Sequence in context: A264362 A160839 A187590 * A036524 A262063 A140934 Adjacent sequences:  A172214 A172215 A172216 * A172218 A172219 A172220 KEYWORD nonn,easy AUTHOR Vaclav Kotesovec, Jan 29 2010 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 20:06 EST 2018. Contains 318245 sequences. (Running on oeis4.)