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 A337559 #17 Sep 28 2020 02:02:11 %S A337559 1,2,3,4,5,18,19,20,21,22,23,36,37,38,51,52,53,66,67,80,81,82,83,96, %T A337559 97,98,99,112,113,138,139,140,141,142,155,168,169,170,171,184,185,210, %U A337559 211,212,237,238,239,252,253,254,255,256,257,270,271,284,285,286,287,324,325,326,339 %N A337559 Number of length three 1..n vectors that contain their harmonic mean. %H A337559 Hywel Normington, <a href="https://github.com/Horep/Number-of-vectors-that-contain-their-average/blob/master/A337559.py">Python code</a>, 2020. %F A337559 Empirical: If A174903(n) = 0, a(n) = a(n-1) + 1. %F A337559 a(n)-a(n-1) = 1 (mod 6). %e A337559 For n = 1, the only solution is (1,1,1). %e A337559 For n = 6, the a(6) = 18 solutions are (k,k,k) for k=1,..,6, the 6 permutations of (2,3,6) and the 6 permutations of (3,4,6). %e A337559 For n = 40, the a(40)-a(39) = 13 new solutions are (40,40,40), the 6 permutations of (10,16,40) and the 6 permutations of (24,30,40). %Y A337559 Cf. A248434, A337110, A337111, A337560. %K A337559 nonn %O A337559 1,2 %A A337559 _Hywel Normington_, Aug 31 2020