Number of reversible strings with n beads using exactly four different colors.
A056311
Number of reversible strings with n beads using exactly four different colors.
Terms
- a(0) =0a(1) =0a(2) =0a(3) =12a(4) =120a(5) =780a(6) =4212a(7) =20424a(8) =93360a(9) =409380a(10) =1749780a(11) =7338792a(12) =30394560a(13) =124705140a(14) =508291812a(15) =2061607224a(16) =8332140720a(17) =33585777060a(18) =135116412660a(19) =542785800072
External references
- oeis: A056311