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 A276720 #9 Sep 22 2016 07:25:58 %S A276720 1,1,2,5,15,37,87,208,515,1271,3112,7594,18578,45510,111464,272839, %T A276720 667809,1634784,4002217,9797781,23985131,58715973,143739040,351879841, %U A276720 861416293,2108779100,5162371032,12637686756,30937555540,75736343956,185405513889,453879917561 %N A276720 Number of set partitions of [n] such that for each block b the smallest integer interval containing b has at most four elements. %H A276720 Alois P. Heinz, <a href="/A276720/b276720.txt">Table of n, a(n) for n = 0..1000</a> %H A276720 Wikipedia, <a href="https://en.wikipedia.org/wiki/Partition_of_a_set">Partition of a set</a> %F A276720 G.f.: -(x-1)*(x+1)/(x^8+3*x^7-5*x^5-5*x^4-x^3-2*x^2-x+1). %Y A276720 Column k=4 of A276719. %Y A276720 Cf. A276838, A276894. %K A276720 nonn,easy %O A276720 0,3 %A A276720 _Alois P. Heinz_, Sep 16 2016