Numbers a(n) with property a(n) + a(n+4) = 2^(n+4) - 1 = A000225(n+4).

Terms

a(0) =0a(1) =1a(2) =3a(3) =7a(4) =15a(5) =30a(6) =60a(7) =120a(8) =240a(9) =481a(10) =963a(11) =1927a(12) =3855a(13) =7710a(14) =15420a(15) =30840a(16) =61680a(17) =123361a(18) =246723a(19) =493447a(20) =986895a(21) =1973790a(22) =3947580a(23) =7895160a(24) =15790320a(25) =31580641a(26) =63161283a(27) =126322567a(28) =252645135a(29) =505290270