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

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =4a(5) =0a(6) =-16a(7) =-64a(8) =-192a(9) =-512a(10) =-1280a(11) =-3072a(12) =-7168a(13) =-16384a(14) =-36864a(15) =-81920a(16) =-180224a(17) =-393216a(18) =-851968a(19) =-1835008a(20) =-3932160a(21) =-8388608a(22) =-17825792a(23) =-37748736a(24) =-79691776a(25) =-167772160a(26) =-352321536a(27) =-738197504a(28) =-1543503872a(29) =-3221225472