Number of bracelets (turn over necklaces) with n red, 1 pink and n-1 blue beads; also reversible strings with n red and n-1 blue beads; also next-to-central column in Losanitsch's triangle A034851.
A005654
Number of bracelets (turn over necklaces) with n red, 1 pink and n-1 blue beads; also reversible strings with n red and n-1 blue beads; also next-to-central column in Losanitsch's triangle A034851.
Terms
- a(0) =1a(1) =2a(2) =6a(3) =19a(4) =66a(5) =236a(6) =868a(7) =3235a(8) =12190a(9) =46252a(10) =176484a(11) =676270a(12) =2600612a(13) =10030008a(14) =38781096a(15) =150273315a(16) =583407990a(17) =2268795980a(18) =8836340260a(19) =34461678394a(20) =134564560988a(21) =526024917288
External references
- oeis: A005654