Number of chiral pairs of color loops of length n with exactly 3 different colors.

Terms

a(0) =0a(1) =0a(2) =1a(3) =3a(4) =12a(5) =35a(6) =111a(7) =318a(8) =934a(9) =2634a(10) =7503a(11) =21071a(12) =59472a(13) =167229a(14) =472133a(15) =1333263a(16) =3777600a(17) =10721837a(18) =30516447a(19) =87035631a(20) =248820816a(21) =712751271a(22) =2045784183a(23) =5882388956a(24) =16942974060a(25) =48876617790a(26) =141204945463a(27) =408495109005