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 A199769 #15 Jul 22 2025 13:23:25
%S A199769 1,2,3,4,4,5,5,5,6,6,6,6,6,6,7,7,7,7,7,7,7,7,7,7,7,7,8,8,8,8,8,8,8,8,
%T A199769 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
%U A199769 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,10
%N A199769 Number of brackets in distinct sets with fewest possible elements.
%H A199769 Alois P. Heinz, <a href="/A199769/b199769.txt">Table of n, a(n) for n = 1..11306</a>
%F A199769 a(n) = A198759(n+1) - A198759(n).
%e A199769 There are three repetitions of 5 because of the sets {{{{{}}}}}, {{{}, {{}}}}, and {{{{}}}, {}}.
%p A199769 b:= proc(n) a(n):= `if`(n<2, n, add(a(n-k)*add(b(d)*d*
%p A199769 (-1)^(k/d+1), d=numtheory[divisors](k)), k=1..n-1)/(n-1))
%p A199769 end:
%p A199769 T:= n-> n$b(n):
%p A199769 seq(T(n), n=1..10); # _Alois P. Heinz_, May 05 2023
%Y A199769 Differences of A198759. Also n repeated A004111(n) times.
%K A199769 nonn
%O A199769 1,2
%A A199769 _Joshua Zucker_, Nov 10 2011
%E A199769 Second set in example corrected by _Rick L. Shepherd_, May 22 2013