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Research notes on every problem, and a library of the papers behind them. Built from the open erdos repository.

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Source. Published p. 590, Table 2 and the paragraph before it; the search method is on p. 589.

Statement. Table 2, headed as the smallest element of SnS_n with its factorization, lists a value knk_n for each 1≤n≤201\le n\le20, with SnS_n the set defined on Theorem 2.1. For n≤16n\le16 the paper reports knk_n as the least element of SnS_n, computed with the criterion of Theorem 2.1; for n=17n=17 a search over k≤108k\le10^8 found no element (p. 590). The rows 17≤n≤2017\le n\le20 carry an asterisk: the paper found these elements of SnS_n through Conjecture 3.8 (p. 595), expects them to be the least, and did not check that. Row nn answers Problem 389 at n+1n+1:

Paper's nnProblem 389's nnkk
112255
223344
3344207207
4455206206
556624752475
6677984984
778881718171
889981708170
9910104514445144
101011114514345143
1111121236488303648830
1212131336488293648829
1313141479790777979077
1414151579790767979076
151516165806886258068862
161617175806886158068861
17171818339949235∗339949235^*
18181919339949234∗339949234^*
191920201019547825∗1019547825^*
202021211019547824∗1019547824^*

The starred values for n=17n=17 and n=19n=19 are z8−17z_8-17 and z9−19z_9-19 for the values z8z_8 and z9z_9 of Table 4, and those for n=18n=18 and n=20n=20 are one less, the pattern of Conjecture 2.11 (k2n−1−1∈S2nk_{2n-1}-1\in S_{2n}). The abstract (p. 583) states the outcome as a positive answer to Question 1.1 for each n≤20n\le20.

Proof pointer. A computer search (p. 589): for each candidate kk and each j≤nj\le n, the primes dividing k+jk+j are found, and the inequality of Theorem 2.1 is tested at each of them.

Dependencies. Theorem 2.1; for the starred rows, Table 4 and Conjecture 3.8 as the means of finding them.

Read depth. Claims checked: the table and the account of the search were read on the page images. No entry was recomputed and no search was rerun, so the minimality for n≤16n\le16 and the membership of the starred values rest on the paper's report. Nothing here is independently reviewed.

Bears on. #389: the table reports a witness kk for each of the problem's nn from 22 to 2121, the least one for n≤17n\le17; at the problem's n=1n=1 every kk works. These are instances only: the problem asks about every nn.