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 A289172 #11 Aug 26 2017 08:23:42
%S A289172 1,1,2,3,2,3,4,5,6,3,5,7,2,4,5,7,8,3,7,9,6,10,5,7,11,6,10,12,3,5,9,11,
%T A289172 13,14,15,6,10,12,14,15,5,7,11,13,17,6,10,12,14,15,18,3,7,9,11,13,17,
%U A289172 19,10,20,15,21,6,10,12,14,15,18,20,21,22,5,7,11
%N A289172 Irregular triangle read by rows: row n lists terms m of A038566(n) such that A001221(m) = A051265(n), with a(1) = 1.
%C A289172 Consider A051265(n), the largest value of A001221(m) for 1 <= m <= n such that gcd(m, n) = 1 (i.e., m is in the reduced residue system or RRS of n, or m is a totative of n). Row n of this sequence consists of m in RRS(n) such that omega(m) = A051265(n).
%H A289172 Michael De Vlieger, <a href="/A289172/b289172.txt">Table of n, a(n) for the first 1000 rows, flattened</a>
%e A289172 Triangle begins:
%e A289172 n T(n,m) A051265(n)
%e A289172 1: 1 0
%e A289172 2: 1 0
%e A289172 3: 2 1
%e A289172 4: 3 1
%e A289172 5: 2 3 4 1
%e A289172 6: 5 1
%e A289172 7: 6 2
%e A289172 8: 3 5 7 1
%e A289172 9: 2 4 5 7 8 1
%e A289172 10: 3 7 9 1
%e A289172 11: 6 10 2
%e A289172 12: 5 7 11 1
%e A289172 13: 6 10 12 2
%e A289172 14: 3 5 9 11 13 1
%e A289172 15: 14 2
%e A289172 16: 15 2
%e A289172 17: 6 10 12 14 15 2
%e A289172 18: 5 7 11 13 17 1
%e A289172 19: 6 10 12 14 15 18 2
%e A289172 20: 3 7 9 11 13 17 19 1
%t A289172 Table[MaximalBy[#, Last][[All, 1]] &@ Map[{#, PrimeNu@ #} &, Cases[Range[n - 1], k_ /; CoprimeQ[n, k]]] /. {} -> {1}, {n, 30}] // Flatten (* _Michael De Vlieger_, Aug 11 2017 *)
%Y A289172 Cf. A001221, A002110, A038566, A048597, A051250, A051265, A051266, A051267, A051268.
%K A289172 nonn,easy,tabf
%O A289172 1,3
%A A289172 _Michael De Vlieger_, Aug 11 2017