Sub GSER(GAMSER, A, X, GLN)
    ITMAX = 100
    EPS = 0.0000003
    GLN = GAMMLN(A)
    If X <= 0# Then
        If X < 0# Then
            Print " PAUSE"
            Exit Sub
        End If
        GAMSER = 0#
        Exit Sub
    End If
    AP = A
    Sum = 1# / A
    DEL = Sum
    For N = 1 To ITMAX
        AP = AP + 1#
        DEL = DEL * X / AP
        Sum = Sum + DEL
        If Abs(DEL) < Abs(Sum) * EPS Then GoTo 1
    Next N
    Print "A too large, ITMAX too small"
1   GAMSER = Sum * Exp(-X + A * Log(X) - GLN)
End Sub