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Let and denote the least th power nonresidue of . Is it true that
for some constant ?
Let and, for primes , let denote the least th power nonresidue of ; set for every other prime. Is it true that
for some constant ?
Source: erdosproblems.com/980
An accepted solution exists. The statement is true.
PROVED on erdosproblems.com, crediting Elliott [El67b], who proved the asymptotic for every under the convention of the precise Statement, with a constant given as an explicit prime series when is an odd prime (claim page (Elliott, 1967)), after Erdős [Er61e] had proved the case (claim page (Erdős, 1961)) and conjectured the general one. The label describes the precise Statement; the variant under Formulation stays open for composite .
The site's wording defines as the least th power nonresidue of for every prime , as Erdős's texts do ((79) of [Er65b], the site's source, printed p. 232; conjecture (4) of [Er61e], p. 11), and leaves it undefined at the primes with , which have no th power nonresidue. Read as a sum over the primes that have one, it includes, for composite , the primes with , whose least th power nonresidue is ; for prime only the primes contribute. Elliott [El67b] defines in the paper's introduction for and sets for every other prime, and the paper's Theorem 1 proves the asymptotic under that convention for every (indeed with any exponent in place of , and with the explicit constant over the primes when is an odd prime). The site labels the problem PROVED and its commentary says "The general case was proved by Elliott [El67b]", without remarking on the convention. The curator therefore reads the sum as Elliott does, and the precise Statement adopts Elliott's convention. The change inserts Elliott's definition of ; nothing else changes. For prime the two readings agree, since a prime then has every residue a th power. For composite they differ: under the precise Statement the problem is proved for every by Elliott's Theorem 1 (claim page (Elliott, 1967)); under the site's wording the contribution of the primes with is covered by no recorded source, so that reading is open for composite and is recorded as a variant under Formulation. Erdős [Er61e] proved the case , where the readings agree, with (claim page (Erdős, 1961)). The curator's reading is inferred from the label and the credit alone; no text of the curator's states the convention.