The two-term supercongruence conjecture for the original sporadic sequences

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Let A(n)A(n) be one of the 15 original sporadic sequences. For a prime p≥5p\geq 5 and integers m,r≥1m,r\geq 1, write

A(mpr)≡A(mpr−1)(modpλr).A(mp^r) \equiv A(mp^{r-1}) \pmod{p^{\lambda r}}.

Here λ=3\lambda=3 except for the sequences B\bf{B}, C\bf{C}, E\bf{E}, F\bf{F} and s18s_{18}, for which λ=2\lambda=2.

Two-term supercongruence conjecture. For all primes p≥5p\geq 5 and all integers m,r≥1m,r\geq 1,

A(mpr)≡A(mpr−1)(modpλr).A(mp^r) \equiv A(mp^{r-1}) \pmod{p^{\lambda r}}.

The conjecture concerns the arithmetic properties of the 15 sporadic sequences, which arise from three-term recurrences and have modular parametrizations, binomial-sum representations and geometric origins. The paper states that this is the original conjecture and proves the last remaining case, so the claim is solved.

References

Primary source

Brendan Alinquant and Robert Osburn, “On sporadic sequences”, arXiv:2312.07134 (2024).

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