Bounds of fractional tetration












1












$begingroup$


I know about Kneser, but if we take a simple recursion



$$^{1/d}b=c, a(0)=b, a(n)=b^{frac{1}{^{d-1}(a(n-1))}}$$



so



$$limlimits_{ntoinfty}a(n)=c$$



and we can quickly find $c$ for positive integer $d>1$ and positive $b$. But $b$ has bounds, ex.



$$d=2, left[(frac{1}{e})^{frac{1}{e}}; e^eright]$$
$$d=3, [0; approx2,421]$$
$$d=4, [approx0,593; approx1,904]$$
$$d=5, [0; approx1,762]$$
$$d=6, [approx0,543; approx1,689]$$
$$d=7, [0; approx1,632]$$
$$d=8, [approx0,511; approx1,592]$$



What is the law of those bounds? Why is lower bound for odd $d$ is $0$?










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  • 1




    $begingroup$
    How do you define $^xb$ for non-integer $x$?
    $endgroup$
    – Simply Beautiful Art
    Jan 13 at 23:19










  • $begingroup$
    @SimplyBeautifulArt, thank you for comment! If $^xb=c$, so $^{1/x}c=b$.
    $endgroup$
    – user514787
    Jan 14 at 0:17










  • $begingroup$
    That doesn't define it though. And what's to guarantee it's uniqueness?
    $endgroup$
    – Simply Beautiful Art
    Jan 14 at 0:19
















1












$begingroup$


I know about Kneser, but if we take a simple recursion



$$^{1/d}b=c, a(0)=b, a(n)=b^{frac{1}{^{d-1}(a(n-1))}}$$



so



$$limlimits_{ntoinfty}a(n)=c$$



and we can quickly find $c$ for positive integer $d>1$ and positive $b$. But $b$ has bounds, ex.



$$d=2, left[(frac{1}{e})^{frac{1}{e}}; e^eright]$$
$$d=3, [0; approx2,421]$$
$$d=4, [approx0,593; approx1,904]$$
$$d=5, [0; approx1,762]$$
$$d=6, [approx0,543; approx1,689]$$
$$d=7, [0; approx1,632]$$
$$d=8, [approx0,511; approx1,592]$$



What is the law of those bounds? Why is lower bound for odd $d$ is $0$?










share|cite|improve this question











$endgroup$








  • 1




    $begingroup$
    How do you define $^xb$ for non-integer $x$?
    $endgroup$
    – Simply Beautiful Art
    Jan 13 at 23:19










  • $begingroup$
    @SimplyBeautifulArt, thank you for comment! If $^xb=c$, so $^{1/x}c=b$.
    $endgroup$
    – user514787
    Jan 14 at 0:17










  • $begingroup$
    That doesn't define it though. And what's to guarantee it's uniqueness?
    $endgroup$
    – Simply Beautiful Art
    Jan 14 at 0:19














1












1








1





$begingroup$


I know about Kneser, but if we take a simple recursion



$$^{1/d}b=c, a(0)=b, a(n)=b^{frac{1}{^{d-1}(a(n-1))}}$$



so



$$limlimits_{ntoinfty}a(n)=c$$



and we can quickly find $c$ for positive integer $d>1$ and positive $b$. But $b$ has bounds, ex.



$$d=2, left[(frac{1}{e})^{frac{1}{e}}; e^eright]$$
$$d=3, [0; approx2,421]$$
$$d=4, [approx0,593; approx1,904]$$
$$d=5, [0; approx1,762]$$
$$d=6, [approx0,543; approx1,689]$$
$$d=7, [0; approx1,632]$$
$$d=8, [approx0,511; approx1,592]$$



What is the law of those bounds? Why is lower bound for odd $d$ is $0$?










share|cite|improve this question











$endgroup$




I know about Kneser, but if we take a simple recursion



$$^{1/d}b=c, a(0)=b, a(n)=b^{frac{1}{^{d-1}(a(n-1))}}$$



so



$$limlimits_{ntoinfty}a(n)=c$$



and we can quickly find $c$ for positive integer $d>1$ and positive $b$. But $b$ has bounds, ex.



$$d=2, left[(frac{1}{e})^{frac{1}{e}}; e^eright]$$
$$d=3, [0; approx2,421]$$
$$d=4, [approx0,593; approx1,904]$$
$$d=5, [0; approx1,762]$$
$$d=6, [approx0,543; approx1,689]$$
$$d=7, [0; approx1,632]$$
$$d=8, [approx0,511; approx1,592]$$



What is the law of those bounds? Why is lower bound for odd $d$ is $0$?







tetration hyperoperation






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 13 at 23:20









Simply Beautiful Art

50.9k580186




50.9k580186










asked Oct 28 '18 at 11:08









user514787user514787

749410




749410








  • 1




    $begingroup$
    How do you define $^xb$ for non-integer $x$?
    $endgroup$
    – Simply Beautiful Art
    Jan 13 at 23:19










  • $begingroup$
    @SimplyBeautifulArt, thank you for comment! If $^xb=c$, so $^{1/x}c=b$.
    $endgroup$
    – user514787
    Jan 14 at 0:17










  • $begingroup$
    That doesn't define it though. And what's to guarantee it's uniqueness?
    $endgroup$
    – Simply Beautiful Art
    Jan 14 at 0:19














  • 1




    $begingroup$
    How do you define $^xb$ for non-integer $x$?
    $endgroup$
    – Simply Beautiful Art
    Jan 13 at 23:19










  • $begingroup$
    @SimplyBeautifulArt, thank you for comment! If $^xb=c$, so $^{1/x}c=b$.
    $endgroup$
    – user514787
    Jan 14 at 0:17










  • $begingroup$
    That doesn't define it though. And what's to guarantee it's uniqueness?
    $endgroup$
    – Simply Beautiful Art
    Jan 14 at 0:19








1




1




$begingroup$
How do you define $^xb$ for non-integer $x$?
$endgroup$
– Simply Beautiful Art
Jan 13 at 23:19




$begingroup$
How do you define $^xb$ for non-integer $x$?
$endgroup$
– Simply Beautiful Art
Jan 13 at 23:19












$begingroup$
@SimplyBeautifulArt, thank you for comment! If $^xb=c$, so $^{1/x}c=b$.
$endgroup$
– user514787
Jan 14 at 0:17




$begingroup$
@SimplyBeautifulArt, thank you for comment! If $^xb=c$, so $^{1/x}c=b$.
$endgroup$
– user514787
Jan 14 at 0:17












$begingroup$
That doesn't define it though. And what's to guarantee it's uniqueness?
$endgroup$
– Simply Beautiful Art
Jan 14 at 0:19




$begingroup$
That doesn't define it though. And what's to guarantee it's uniqueness?
$endgroup$
– Simply Beautiful Art
Jan 14 at 0:19










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