Van Hamme's supercongruence (A.2) for a truncated hypergeometric series

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Let pp be an odd prime. For parameters a1,,a6a_1,,a_6 and b1,,b5b_1,,b_5, write the truncated hypergeometric series as

6F5[a1,a2,a3,a4,a5,a6b1,b2,b3,b4,b5;z]n=∑k=0n(a1)k(a2)k(a3)k(a4)k(a5)k(a6)k(b1)k(b2)k(b3)k(b4)k(b5)kzkk!,{}_{6}F_{5}\left[ \begin{matrix} a_1,a_2,a_3,a_4,a_5,a_6\\ b_1,b_2,b_3,b_4,b_5\end{matrix};z\right]_n=\sum_{k=0}^n\frac{(a_1)_k(a_2)_k(a_3)_k(a_4)_k(a_5)_k(a_6)_k}{(b_1)_k(b_2)_k(b_3)_k(b_4)_k(b_5)_k}\frac{z^k}{k!},

where (a)0=1(a)_0=1 and (a)k=a(a+1)⋯(a+k−1)(a)_k=a(a+1)\cdots(a+k-1) for k≥1k\geq 1. Let Γp(⋅)\Gamma_p(\cdot) denote the pp-adic Gamma function. Van Hamme's supercongruence (A.2).

6F5[54,12,12,12,12,1214,1,1,1,1;−1]p−12≡{−pΓp(14)4(modp3)if p≡1(mod4),0(modp3)if p≡3(mod4).{}_{6}F_{5}\left[ \begin{matrix} \frac{5}{4},\frac{1}{2},\frac{1}{2},\frac{1}{2},\frac{1}{2},\frac{1}{2}\\ \frac{1}{4},1,1,1,1\end{matrix};-1\right]_{\frac{p-1}{2}}\equiv\begin{cases}-p\Gamma_p\left(\frac{1}{4}\right)^4\pmod{p^3}&\text{if }p\equiv1\pmod{4},\\0\pmod{p^3}&\text{if }p\equiv3\pmod{4}. \end{cases}

The congruence was first confirmed by McCarthy and Osburn, so it is solved rather than open.

References

Primary source

Ji-Cai Liu, “Supercongruences arising from hypergeometric series identities”, arXiv:1812.09101 (2018).

Additional references

2 papers in this index state this conjecture (2009–2018). The statement above is taken from the most recent of them; the others are arXiv:0912.0197.

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