LET maxit = 13
LET maxitj = 13
LET a1 = 1.0
LET d1 = 3.2

PRINT "Feigenbaum constant calculation:"
PRINT
PRINT "  i     d"
PRINT "==================="

FOR i = 2 to maxit
    LET a = a1 + (a1 - a2) / d1
    FOR j = 1 to maxitj
        LET x = 0
        LET y = 0
        FOR k = 1 to 2 ^ i
            LET y = 1 - 2 * y * x
            LET x = a - x * x
        NEXT k
        LET a = a - (x / y)
    NEXT j
    LET d = (a1 - a2) / (a - a1)
    PRINT using "###    ##.#########": i, d
    LET d1 = d
    LET a2 = a1
    LET a1= a
NEXT i
END