Gödel's beta-function lemma

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Consider the Godel function

β(x,y,z)=rest⁡(x,1+y(z+1)). \beta (x, y, z) = \operatorname {rest}(x, 1 + y(z+1)).

Prove that, whatever the finite sequence of natural numbers a1,…,ana_{1}, \ldots , a_{n} may be, the system of equations

{β(x,y,0)=α0,\makebox[0pt][l]\dotfillβ(x,y,n)=αn, \begin{cases} \beta (x, y, 0) = \alpha _{0}, \\ \makebox[0pt][l]{\dotfill } \\ \beta (x, y, n) = \alpha _{n}, \end{cases}

has at least one solution x,yx, y.

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Prove that the function fn+1f^{n+1}, obtained by means of the primitive recursion operator from everywhere defined functions gng^{n} and hn+2h^{n+2}, can be obtained from these functions and the functions +,\symdiff,s,o,Imn+, \symdiff , s, o, I_{m}^{n} and c,l,r,βc, l, r, \beta from problems III.1.13, III.1.17, by means of superpositions and a μ\mu-operator of the special form from problem III.1.29.

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References

[LaMa02] Lavrov I.A., Maksimova L.L. Задачи по теории множеств, математической логике и теории алгоритмов. 5-е изд., Физматлит, 2002.