A202656 Number of ways to place 5 nonattacking semi-queens on an n X n board.

0, 0, 0, 0, 23, 1104, 16945, 141696, 810746, 3568352, 12948318, 40514560, 112720393, 285073712, 666143975, 1456288512, 3007576740, 5913372864, 11138305068, 20202100224, 35433809451, 60316600080, 99947225741, 161638967424, 255701773822, 396439174560, 603407582570

Offset

1,5

Comments

Two semi-queens do not attack each other if they are in the same northwest-southeast diagonal.

Links

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Christopher R. H. Hanusa, Thomas Zaslavsky, A q-queens problem. VII. Combinatorial types of nonattacking chess riders, arXiv:1906.08981 [math.CO], 2019.

V. Kotesovec, Non-attacking chess pieces

Formula

a(n) = n^10/120 - 2*n^9/9 + 95*n^8/36 - 183*n^7/10 + 14663*n^6/180 - 1201*n^5/5 + 16753*n^4/36 - 25364*n^3/45 + 68293*n^2/180 - 12781*n/120 + (n^3/2 - 6*n^2 + 39*n/2 - 61/4)*floor(n/2).

G.f.: -x^5*(1899*x^9 + 16515*x^8 + 60512*x^7 + 116784*x^6 + 137646*x^5 + 98222*x^4 + 41688*x^3 + 9608*x^2 + 943*x + 23)/((x-1)^11*(x+1)^4).

Mathematica

Rest@ CoefficientList[Series[-x^5*(1899 x^9 + 16515 x^8 + 60512 x^7 + 116784 x^6 + 137646 x^5 + 98222 x^4 + 41688 x^3 + 9608 x^2 + 943 x + 23)/((x - 1)^11*(x + 1)^4), {x, 0, 27}], x] (* Michael De Vlieger, Aug 19 2019 *)

Crossrefs

Cf. A099152, A108792, A103220, A202654, A202655, A202657.

Sequence in context: A128404 A126741 A273477 * A367772 A340487 A321569

Adjacent sequences: A202653 A202654 A202655 * A202657 A202658 A202659

Keyword

nonn

Author

Vaclav Kotesovec, Dec 22 2011

Status

approved