Number of cases of tie (no winner) in the n-person rock-paper-scissors game.

Terms

a(0) =3a(1) =3a(2) =9a(3) =39a(4) =153a(5) =543a(6) =1809a(7) =5799a(8) =18153a(9) =55983a(10) =171009a(11) =519159a(12) =1569753a(13) =4733823a(14) =14250609a(15) =42850119a(16) =128746953a(17) =386634063a(18) =1160688609a(19) =3483638679a(20) =10454061753a(21) =31368476703a(22) =94118013009a(23) =282379204839a(24) =847187946153