Number of reversible strings with n beads of 3 colors. If more than 1 bead, not palindromic.

A032086

Number of reversible strings with n beads of 3 colors. If more than 1 bead, not palindromic.

Terms

    a(0) =3a(1) =3a(2) =9a(3) =36a(4) =108a(5) =351a(6) =1053a(7) =3240a(8) =9720a(9) =29403a(10) =88209a(11) =265356a(12) =796068a(13) =2390391a(14) =7171173a(15) =21520080a(16) =64560240a(17) =193700403a(18) =581101209a(19) =1743362676a(20) =5230088028a(21) =15690441231a(22) =47071323693a(23) =141214502520a(24) =423643507560

External references