a(n) is the number of incongruent two-color bracelets of n beads, 10 from them are black (A005515), having a diameter of symmetry.
A189980
a(n) is the number of incongruent two-color bracelets of n beads, 10 from them are black (A005515), having a diameter of symmetry.
Terms
- a(0) =1a(1) =1a(2) =6a(3) =6a(4) =21a(5) =21a(6) =56a(7) =56a(8) =126a(9) =126a(10) =252a(11) =252a(12) =462a(13) =462a(14) =792a(15) =792a(16) =1287a(17) =1287a(18) =2002a(19) =2002a(20) =3003a(21) =3003a(22) =4368a(23) =4368a(24) =6188a(25) =6188a(26) =8568a(27) =8568a(28) =11628a(29) =11628
External references
- oeis: A189980