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

A201222

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

Terms

    a(0) =3a(1) =9a(2) =18a(3) =81a(4) =123a(5) =324a(6) =843a(7) =2401a(8) =5778a(9) =15129a(10) =39603a(11) =104976a(12) =271443a(13) =710649a(14) =1860498a(15) =4879681a(16) =12752043a(17) =33385284a(18) =87403803a(19) =228886641a(20) =599074578a(21) =1568397609a(22) =4106118243a(23) =10750371856a(24) =28143753123a(25) =73681302249a(26) =192900153618a(27) =505022001201

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