Number of 2n-bead black-white strings with n black beads and fundamental period 2n.
A007727
Number of 2n-bead black-white strings with n black beads and fundamental period 2n.
Terms
- a(0) =1a(1) =2a(2) =4a(3) =18a(4) =64a(5) =250a(6) =900a(7) =3430a(8) =12800a(9) =48600a(10) =184500a(11) =705430a(12) =2703168a(13) =10400598a(14) =40113164a(15) =155117250a(16) =601067520a(17) =2333606218a(18) =9075085776a(19) =35345263798a(20) =137846344000a(21) =538257870990
External references
- oeis: A007727