a(n) = 2*a(n - 2) - a(n - 1) for n>1, a(0) = 4, a(1) = 5.

Terms

a(0) =4a(1) =5a(2) =3a(3) =7a(4) =-1a(5) =15a(6) =-17a(7) =47a(8) =-81a(9) =175a(10) =-337a(11) =687a(12) =-1361a(13) =2735a(14) =-5457a(15) =10927a(16) =-21841a(17) =43695a(18) =-87377a(19) =174767a(20) =-349521a(21) =699055a(22) =-1398097a(23) =2796207a(24) =-5592401a(25) =11184815a(26) =-22369617a(27) =44739247a(28) =-89478481a(29) =178956975