First differences of A006921.

Terms

a(0) =0a(1) =2a(2) =-1a(3) =5a(4) =-2a(5) =8a(6) =-5a(7) =21a(8) =-8a(9) =34a(10) =-21a(11) =81a(12) =-34a(13) =128a(14) =-81a(15) =337a(16) =-128a(17) =546a(18) =-337a(19) =1301a(20) =-546a(21) =2056a(22) =-1301a(23) =5381a(24) =-2056a(25) =8706a(26) =-5381a(27) =20737a(28) =-8706a(29) =32768