a(n) = a(n-1) + 2*a(n-2) if n even, or 3*a(n-1) + 4*a(n-2) if n odd, starting with 0, 1.

Terms

a(0) =0a(1) =1a(2) =1a(3) =7a(4) =9a(5) =55a(6) =73a(7) =439a(8) =585a(9) =3511a(10) =4681a(11) =28087a(12) =37449a(13) =224695a(14) =299593a(15) =1797559a(16) =2396745a(17) =14380471a(18) =19173961a(19) =115043767a(20) =153391689a(21) =920350135a(22) =1227133513a(23) =7362801079a(24) =9817068105a(25) =58902408631a(26) =78536544841a(27) =471219269047a(28) =628292358729