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 A177201 #6 Sep 15 2013 00:56:00
%S A177201 6,9,10,12,15,16,18,20,21,22,24,25,27,28,30,32,33,34,35,36,39,40,42,
%T A177201 44,45,46,48,49,50,51,52,54,55,56,57,58,60,63,64,65,66,68,69,70,72,75,
%U A177201 76,78,80,81,82,84,85,87,88,90,91,92,93,94,95,96,98,99,100
%N A177201 Multiples of nontrivially polygonal numbers A090466.
%C A177201 Multiples of numbers in the array of A057145 below the second row (which has every positive integer) and right of the 2nd column (which has every positive integer). That is, multiples of every triangular number >3, every square >4, every pentagonal number >5, every hexagonal number >6, every heptagonal number >7, every octagonal number >8, every 9-gonal (nonagonal) number >9, and so forth.
%C A177201 Nontrivially polygonal numbers {6, 9, 10, 12, 15, 16, 18, 21, 22, 24, 25, 27, 28, 30, 33, 34, 35, 36, 39, 40, 42, 45, 46, 48, 49,...} UNION 2*nontrivially polygonal = {12, 18, 20, 24, 30, 32, 36, 42, 44, 48, 50, 54, 56, 60, 66, 68, 70, 72, 78, 80, 84, 90, 92, 96, 98, ...} UNION 3*nontrivially polygonal = {18, 27, 30, 36, 45, 48, 54, 63, 66, 72, 75, 81, 84, 90, 99, ...} UNION 4*nontrivially polygonal = {24, 36, 40, 48, 60, 64, 72, 84, 88, 96, 100, ...} UNION 5*nontrivially polygonal = {30, 45, 50, 60, 75, 80, 90, ...} UNION 6*nontrivially polygonal = {36, 54, 60, 72, 90, 96, ...} UNION 7*nontrivially polygonal = {42, 63, 70, 84, ...} and so forth.
%F A177201 {A057145 * j for j = 1, 2, 3, 4, 5, ...} = {j * ((n-2)*k^2-(n-4)*k)/2, j>0, n > 2, k > 2}.
%Y A177201 Cf. A057145, A090466, complement is A177202.
%K A177201 easy,nonn
%O A177201 1,1
%A A177201 _Jonathan Vos Post_, May 04 2010