Number of n-digit biquanimous strings using digits {0,1,2,3}.

Terms

a(0) =1a(1) =1a(2) =4a(3) =19a(4) =92a(5) =421a(6) =1830a(7) =7687a(8) =31624a(9) =128521a(10) =518666a(11) =2084875a(12) =8361996a(13) =33497101a(14) =134094862a(15) =536608783a(16) =2146926608a(17) =8588754961a(18) =34357248018a(19) =137433710611a(20) =549744803860