a(n) = 3*a(n-1) + a(n-2) - a(n-3) for n >= 3, a(0)=1, a(1)=2, a(2)=7.

Terms

a(0) =1a(1) =2a(2) =7a(3) =22a(4) =71a(5) =228a(6) =733a(7) =2356a(8) =7573a(9) =24342a(10) =78243a(11) =251498a(12) =808395a(13) =2598440a(14) =8352217a(15) =26846696a(16) =86293865a(17) =277376074a(18) =891575391a(19) =2865808382a(20) =9211624463a(21) =29609106380a(22) =95173135221a(23) =305916887580a(24) =983314691581