Type X Ramanujan-type series identity for 1/π with T_k(19,−20) and T_{2k}(9,−5)
Prove that the infinite series sum_{k=0}^∞ [(16k+3)/(-202^2)^k] * binom(2k,k) * T_k(19,-20) * T_{2k}(9,-5) equals 43√101/(75π), where T_n(b,c) denotes the coefficient of x^n in (x^2 + b x + c)^n.
References
For example, we conjecture that $$\sum_{k=0}\infty\frac{16k+3}{(-2022)k} \binom{2k}kT_k(19,-20)T_{2k}(9,-5)=\frac{43\sqrt{101}{75\pi},$$ where $T_n(b,c)$ denotes the coefficient of $xn$ in the expansion of $(x2+bx+c)n$.
— Various conjectural series identities
(2603.29973 - Sun, 31 Mar 2026) in Abstract, page 1