A007318 * [1, 1, -1, 1, 1, 1, ...].

Terms

a(0) =1a(1) =2a(2) =2a(3) =2a(4) =4a(5) =12a(6) =34a(7) =86a(8) =200a(9) =440a(10) =934a(11) =1938a(12) =3964a(13) =8036a(14) =16202a(15) =32558a(16) =65296a(17) =130800a(18) =261838a(19) =523946a(20) =1048196a(21) =2096732a(22) =4193842a(23) =8388102a(24) =16776664a(25) =33553832a(26) =67108214a(27) =134217026a(28) =268434700a(29) =536870100