Number of irreducible words of length 2n in the free group with generators x,y such that the total degree of x and the total degree of y both equal zero.
A007987
Number of irreducible words of length 2n in the free group with generators x,y such that the total degree of x and the total degree of y both equal zero.
Terms
- a(0) =1a(1) =0a(2) =8a(3) =40a(4) =312a(5) =2240a(6) =17280a(7) =134568a(8) =1071000a(9) =8627872a(10) =70302888a(11) =577920200a(12) =4786740112a(13) =39899052960a(14) =334391846048
External references
- oeis: A007987