Column 1 of triangle A055325.A055326Column 1 of triangle A055325.Terms a(0) =1a(1) =-1a(2) =3a(3) =-23a(4) =425a(5) =-18129a(6) =1721419a(7) =-353654167a(8) =153923102577External referencesoeis: A055326