k=1n+1(n+1)!(k-1)!(n-k+1)!(-a-n)kzn-k+1-k=0-a-n-1(a+n+1)k(n+2)kk!zn+k+1(lnz+ψ(-a-n-k)-ψ(1+k)-ψ(n+k+2))+(-1)n-a(-a-n-1)!k=-a-n(k+a+n)!(n+2)kk!zn+k+1,