A generalized Jacobsthal sequence.

Terms

a(0) =0a(1) =1a(2) =-1a(3) =-1a(4) =-5a(5) =-9a(6) =-21a(7) =-41a(8) =-85a(9) =-169a(10) =-341a(11) =-681a(12) =-1365a(13) =-2729a(14) =-5461a(15) =-10921a(16) =-21845a(17) =-43689a(18) =-87381a(19) =-174761a(20) =-349525a(21) =-699049a(22) =-1398101a(23) =-2796201a(24) =-5592405a(25) =-11184809a(26) =-22369621a(27) =-44739241a(28) =-89478485a(29) =-178956969