Number of length-n 0..3 arrays connected end-around, with no sequence of L<n elements immediately followed by itself (periodic "squarefree").
A215223
Number of length-n 0..3 arrays connected end-around, with no sequence of L<n elements immediately followed by itself (periodic "squarefree").
Terms
- a(0) =4a(1) =12a(2) =24a(3) =72a(4) =120a(5) =408a(6) =840a(7) =2448a(8) =5760a(9) =15960a(10) =39864a(11) =108024a(12) =275184a(13) =728784a(14) =1895760a(15) =4998528a(16) =13033560a(17) =34250904a(18) =89602632a(19) =235157640a(20) =615871032
External references
- oeis: A215223