Number of 2-divided words of length n over a 3-letter alphabet.

Terms

a(0) =0a(1) =3a(2) =16a(3) =57a(4) =192a(5) =599a(6) =1872a(7) =5727a(8) =17488a(9) =53115a(10) =161040a(11) =487073a(12) =1471680a(13) =4441167a(14) =13392272a(15) =40355877a(16) =121543680a(17) =365895947a(18) =1101089808a(19) =3312442185a(20) =9962240928a(21) =29954639751a(22) =90049997136a(23) =270661616363a(24) =813397065024