a(n) = A006496(n)/2.

Terms

a(0) =0a(1) =1a(2) =2a(3) =-1a(4) =-12a(5) =-19a(6) =22a(7) =139a(8) =168a(9) =-359a(10) =-1558a(11) =-1321a(12) =5148a(13) =16901a(14) =8062a(15) =-68381a(16) =-177072a(17) =-12239a(18) =860882a(19) =1782959a(20) =-738492a(21) =-10391779a(22) =-17091098a(23) =17776699a(24) =121008888a(25) =153134281a(26) =-298775878a(27) =-1363223161a(28) =-1232566932