Number of n-bead necklaces labeled with numbers -1..1 not allowing reversal, with sum zero and avoiding the patterns z z+1 z+2 and z z-1 z-2.
A209108
Number of n-bead necklaces labeled with numbers -1..1 not allowing reversal, with sum zero and avoiding the patterns z z+1 z+2 and z z-1 z-2.
Terms
- a(0) =1a(1) =2a(2) =1a(3) =5a(4) =5a(5) =15a(6) =25a(7) =68a(8) =139a(9) =354a(10) =813a(11) =2047a(12) =4935a(13) =12421a(14) =30833a(15) =78102a(16) =197139a(17) =503132a(18) =1284711a(19) =3302155a(20) =8503965a(21) =21996761a(22) =57026957a(23) =148322398a(24) =386626825a(25) =1010375144a(26) =2645762431a(27) =6942725217a(28) =18251279163a(29) =48065184969
External references
- oeis: A209108