A201222 Number of ways to place k non-attacking knights on a 2 X n horizontal cylinder, summed over all k>=0.

3, 9, 18, 81, 123, 324, 843, 2401, 5778, 15129, 39603, 104976, 271443, 710649, 1860498, 4879681, 12752043, 33385284, 87403803, 228886641, 599074578, 1568397609, 4106118243, 10750371856, 28143753123, 73681302249, 192900153618, 505022001201, 1322157322203

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

V. Kotesovec, Non-attacking chess pieces

Mathematica

Table[If[Mod[n, 4]==0, LucasL[n/2]^4, LucasL[2n]+1+(-1)^n], {n, 1, 50}]

Crossrefs

Cf. A189145, A001333, A051927, A006506, A067966.

Sequence in context: A190905 A133136 A161138 * A349453 A067864 A272513

Adjacent sequences: A201219 A201220 A201221 * A201223 A201224 A201225

Keyword

nonn,easy

Author

Vaclav Kotesovec, Nov 28 2011

Status

approved