Third differences of the Jacobsthal sequence A001045.

Terms

a(0) =3a(1) =-2a(2) =4a(3) =0a(4) =8a(5) =8a(6) =24a(7) =40a(8) =88a(9) =168a(10) =344a(11) =680a(12) =1368a(13) =2728a(14) =5464a(15) =10920a(16) =21848a(17) =43688a(18) =87384a(19) =174760a(20) =349528a(21) =699048a(22) =1398104a(23) =2796200a(24) =5592408a(25) =11184808a(26) =22369624a(27) =44739240a(28) =89478488a(29) =178956968