Second differences of Jacobsthal sequence A001045, pairs with even and odd indices swapped.

Terms

a(0) =2a(1) =-1a(2) =4a(3) =0a(4) =12a(5) =4a(6) =44a(7) =20a(8) =172a(9) =84a(10) =684a(11) =340a(12) =2732a(13) =1364a(14) =10924a(15) =5460a(16) =43692a(17) =21844a(18) =174764a(19) =87380a(20) =699052a(21) =349524a(22) =2796204a(23) =1398100a(24) =11184812a(25) =5592404a(26) =44739244a(27) =22369620a(28) =178956972a(29) =89478484