This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A338338 #19 Oct 28 2020 18:03:53 %S A338338 1,2,4,6,3,9,5,10,20,8,7,14,28,12,15,30,40,16,11,22,44,18,21,42,56,24, %T A338338 27,33,55,110,50,26,13,39,36,48,32,17,34,68,38,19,57,45,60,70,84,63, %U A338338 51,85,170,80,46,23,69,54,66,88,77,35,105,75,72,52,78,117 %N A338338 Lexicographically earliest infinite sequence of distinct positive numbers such that for any prime p, any run of consecutive multiples of p has length exactly 3. %C A338338 If a prime p divides a(n), then there is a run of exactly three terms (one of which is a(n)) that are divisible by p. %C A338338 If "three" is changed to "two", we get A280864. %C A338338 Conjecture: This is a permutation of the positive integers. %H A338338 Rémy Sigrist, <a href="/A338338/b338338.txt">Table of n, a(n) for n = 1..20000</a> %H A338338 Rémy Sigrist, <a href="/A338338/a338338.gp.txt">PARI program for A338338</a> %e A338338 After 1,2,4,6,3, we have had two successive multiples of 3, so the next term must be a multiple of 3 we have not yet seen, hence 9. The following term is then the smallest number not yet seen which is not a multiple of 3, hence 5. %o A338338 (PARI) See Links section. %Y A338338 A338339-A338349, A338440, A338449, A338450, and A338451 analyze this sequence from various points of view. %Y A338338 Cf. A280864, A338441. %K A338338 nonn %O A338338 1,2 %A A338338 _N. J. A. Sloane_, Oct 27 2020 %E A338338 Corrected and extended by _Rémy Sigrist_, Oct 27 2020