a(2n)=A001896(n). a(2n+1)=(-1)^n*A110501(n+1).

Terms

a(0) =1a(1) =1a(2) =-1a(3) =-1a(4) =7a(5) =3a(6) =-31a(7) =-17a(8) =127a(9) =155a(10) =-2555a(11) =-2073a(12) =1414477a(13) =38227a(14) =-57337a(15) =-929569a(16) =118518239a(17) =28820619a(18) =-5749691557a(19) =-1109652905a(20) =91546277357a(21) =51943281731