a(n) is n-th term of the Euler transform of -n,1,1,1,... .

Terms

a(0) =1a(1) =-1a(2) =2a(3) =-3a(4) =5a(5) =-9a(6) =18a(7) =-39a(8) =88a(9) =-200a(10) =449a(11) =-988a(12) =2131a(13) =-4527a(14) =9540a(15) =-20090a(16) =42510a(17) =-90596a(18) =194299a(19) =-418105a(20) =899493a(21) =-1929000a(22) =4116944a(23) =-8742002a(24) =18484225a(25) =-38974978a(26) =82086786a(27) =-172927251a(28) =364700265a(29) =-770223900