Alternating sum transform (PSumSIGN) of A000975.

Terms

a(0) =1a(1) =1a(2) =4a(3) =6a(4) =15a(5) =27a(6) =58a(7) =112a(8) =229a(9) =453a(10) =912a(11) =1818a(12) =3643a(13) =7279a(14) =14566a(15) =29124a(16) =58257a(17) =116505a(18) =233020a(19) =466030a(20) =932071a(21) =1864131a(22) =3728274a(23) =7456536a(24) =14913085a(25) =29826157a(26) =59652328a(27) =119304642a(28) =238609299