Naturally solving the sexp
#1
The Abel equation for the slog was \( \text{slog}_b(b^x)=\text{slog}_b(x)+1 \).
Our original recurring for the super exponential (which I will call similarly) sexp is \( \text{sexp}_b(x+1)=b^{\text{sexp}_b(x)} \).

So if we develop it at 0, say \( \text{sexp}_b(x)=\sum_{n=0}^\infty \rho_n x^n \) satisfying the inverted Abel equation:
\( \sum_{n=0}^\infty \rho_n (x+1)^n = \exp\left(\log(b)\sum_{n=0}^\infty \rho_n x^n\right) \)
we get
\( \sum_{n=0}^\infty \rho_n \sum_{k=0}^n \left(n\\k\right) x^k = 1 + \sum_{n=0}^\infty B(\log(b)\rho_1,\dots,\log(b)\rho_n) \frac{x^n}{n!} \)
where \( B(x_1,\dots,x_n) \) is the complete Bell polynomial.
The left side develops to \( \sum_{k=0}^\infty x^k \sum_{n=k}^\infty \rho_n \left(n\\k\right) \) and so we have the infinite equation system

\( \sum_{i=k}^\infty \rho_i \left(i\\k\right) = B(\log(b)\rho_1,\dots,\log(b)\rho_k) \frac{1}{k!} \)

And I wonder if we solve it the natural way whether we get exactly the inverse of the slog (which I assume). Unfortunately there is no complete Bell polynomial in Maple (at least I didnt find it) and I am too lazy in the moment to program it myself Wink

And yes, it is not a linear equation system. Perhaps it is despite solvable, who knows ...
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Messages In This Thread
Naturally solving the sexp - by bo198214 - 08/21/2007, 06:41 PM
RE: Naturally solving the sexp - by jaydfox - 08/22/2007, 03:15 AM
RE: Naturally solving the sexp - by Gottfried - 08/22/2007, 08:58 AM

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