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 A304391 #14 Jun 05 2018 10:17:56 %S A304391 6,12,20,24,30,42,56,60,72,90,105,110,120,132,140,156,168,180,182,210, %T A304391 240,252,272,280,306,336,342,360,380,420,462,495,504,506,552,560,600, %U A304391 630,650,660,702,720,756,812,840,858,870,930,990,992,1056,1092,1120,1122,1190 %N A304391 Numbers that are the number of permutations of a set of balls of at least three distinct colors. %F A304391 A027480(k) = k * (k + 1) * (k + 2) / 2 is in the sequence for k >= 2. %e A304391 There are 30 permutations of 5 balls where 2 are red, 2 are yellow and 1 is blue. %Y A304391 A002378 is a subsequence. %Y A304391 Cf. A027480, A304938. %K A304391 nonn,easy %O A304391 1,1 %A A304391 _David A. Corneth_, May 24 2018