Define an array by Q(m, 0) = 1, Q(m, 1) = 1; Q(m, 2k) = (m - 2k + 1)*Q(m+1, 2k-1) - (2k-1)*Q(m+2, 2k-2), m*Q(m, 2k+1) = (m - 2k)*Q(m+1, 2k) - 2k(m+1)*Q(m+2, 2k-1). Sequence gives Q(0,n).

A127137

Define an array by Q(m, 0) = 1, Q(m, 1) = 1; Q(m, 2k) = (m - 2k + 1)*Q(m+1, 2k-1) - (2k-1)*Q(m+2, 2k-2), m*Q(m, 2k+1) = (m - 2k)*Q(m+1, 2k) - 2k(m+1)*Q(m+2, 2k-1). Sequence gives Q(0,n).

Terms

    a(0) =1a(1) =1a(2) =-2a(3) =-5a(4) =12a(5) =43a(6) =-120a(7) =-531a(8) =1680a(9) =8601a(10) =-30240a(11) =-172965a(12) =665280a(13) =4161555a(14) =-17297280a(15) =-116658675a(16) =518918400a(17) =3735104625a(18) =-17643225600a(19) =-134498225925a(20) =670442572800

External references