The q-tangent continued-fraction conjecture for parameter tuple (1,1,1,−1)(1,1,1,-1)

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Let qq be a parameter and let tan⁡q(z)\tan_q(z) denote the q-tangent function. For the parameter tuple (A,B,C,D)=(1,1,1,−1)(A,B,C,D)=(1,1,1,-1), consider the continued fraction

tan⁡q(z)=z[1]qq−0−z2[3]qq0−z2[5]qq−5−z2[7]qq3−z2⋱.\tan_q(z)=\cfrac{z}{[1]_q q^{-0}-\cfrac{z^2}{[3]_q q^{0}-\cfrac{z^2}{[5]_q q^{-5}-\cfrac{z^2}{[7]_q q^{3}-\cfrac{z^2}{\ddots}}}}}.

Continued-fraction conjecture. The positive powers of qq follow the sequence 0,3,10,21,…0,3,10,21,\dots, given by (k−1)(2k−1)(k-1)(2k-1), while the negative powers follow 0,5,14,27,…0,5,14,27,\dots, given by (k−1)(2k+1)(k-1)(2k+1).

This conjecture predicts a further continued-fraction pattern for the q-tangent function. The supplied text gives no proof or resolution, so the conjecture remains open.

References

Primary source

Helmut Prodinger, “Combinatorics of geometrically distributed random variables: New q-tangent and q-secant numbers”, arXiv:math/9910096 (1999).

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