Function BESSY(N, X)
    If N < 2 Then
        Print "bad argument N in BESSY"
        Exit Function
    End If
    TOX = 2# / X
    By = BESSY1(X)
    BYM = BESSY0(X)
    For J = 1 To N - 1
        BYP = J * TOX * By - BYM
        BYM = By
        By = BYP
    Next J
    BESSY = By
End Function