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 A322880 #5 Dec 29 2018 18:10:43 %S A322880 0,1,67,1059,11373,106256,940608,8193031,71568443,633413486, %T A322880 5710573774,52579554510,494986212033,4766754646529,46966622143740, %U A322880 473477764449909,4883216510830794,51513192445470426,555667122424414886,6127026713823497897,69034256792655555566 %N A322880 Number of set partitions of [n] such that the maximal absolute difference between the least elements of consecutive blocks equals seven. %H A322880 Alois P. Heinz, <a href="/A322880/b322880.txt">Table of n, a(n) for n = 7..580</a> %H A322880 Wikipedia, <a href="https://en.wikipedia.org/wiki/Partition_of_a_set">Partition of a set</a> %F A322880 a(n) = A287257(n) - A287256(n). %p A322880 b:= proc(n, k, m, l) option remember; `if`(n<1, 1, %p A322880 `if`(l-n>k, 0, b(n-1, k, m+1, n))+m*b(n-1, k, m, l)) %p A322880 end: %p A322880 A:= (n, k)-> b(n-1, min(k, n-1), 1, n): %p A322880 a:= n-> (k-> A(n, k)-A(n, k-1))(7): %p A322880 seq(a(n), n=7..30); %Y A322880 Column k=7 of A287215. %Y A322880 Cf. A287256, A287257. %K A322880 nonn %O A322880 7,3 %A A322880 _Alois P. Heinz_, Dec 29 2018