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 A309108 #70 Mar 19 2025 18:17:48 %S A309108 1,1,1,2,3,2,5,6,7,4,10,9,7,11,12,8,13,11,17,19,15,23,7,14,16,12,27, %T A309108 13,25,29,31,37,33,30,26,16,20,27,34,29,35,18,41,43,47,53,39,37,49,51, %U A309108 59,38,40,41,46,47,42,19,31,44,55,56,61,57,67,64,45,71,62 %N A309108 Lexicographically earliest sequence such that the product a(j)*a(j+k)*a(j+2k) for any j and k is a unique positive integer. %C A309108 This sequence has an infinite number of terms. The upper bound for any term n > 3 is prime(n-3). %H A309108 Rémy Sigrist, <a href="/A309108/b309108.txt">Table of n, a(n) for n = 0..1000</a> %H A309108 Rémy Sigrist, <a href="/A309108/a309108.gp.txt">PARI program for A309108</a> %e A309108 a(4)*a(7)*a(10) = 3*6*10 = 180. These are the only three equally-spaced terms whose product comes out to be 180. %o A309108 (PARI) \\ See Links section. %K A309108 nonn %O A309108 0,4 %A A309108 _Aaron Kemats_, Sep 03 2019 %E A309108 Data corrected and incorrect program removed by _Rémy Sigrist_, Apr 10 2021