Number of n-bead asymmetric bracelets with exactly 3 different colored beads.

Terms

a(0) =0a(1) =0a(2) =1a(3) =3a(4) =12a(5) =34a(6) =111a(7) =315a(8) =933a(9) =2622a(10) =7503a(11) =21033a(12) =59472a(13) =167118a(14) =472120a(15) =1332945a(16) =3777600a(17) =10720869a(18) =30516447a(19) =87032994a(20) =248820704a(21) =712743768a(22) =2045784183a(23) =5882367570a(24) =16942974048a(25) =48876558318a(26) =141204944529a(27) =408494941773