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 A086984 #15 Sep 14 2024 01:39:35
%S A086984 1,6,60,696,9120,134640,2227680,41005440,833172480,18546796800,
%T A086984 449223667200,11766674304000,331501679308800,9997170543360000,
%U A086984 321355745238528000,10969253822951424000,396269940892041216000
%N A086984 Number of arrangements of n labeled balls in n labeled columns where only 1 column may have more than 1 ball.
%C A086984 The difference between A000407 and A086984 is for example consider a(5). A000407 allows the 221 and 23 partitions, A086984 does not.
%H A086984 Harvey P. Dale, <a href="/A086984/b086984.txt">Table of n, a(n) for n = 1..402</a>
%F A086984 a(n) = n! + Sum_{i=2..n} binomial(n-1, n-i)*n*n!.
%e A086984 a(2)=6;
%e A086984 .. .. -G -R R- G-
%e A086984 RG GR -R -G G- R-
%t A086984 Table[n!+Sum[Binomial[n-1,n-k],{k,2,n}]n n!,{n,20}] (* _Harvey P. Dale_, Nov 29 2019 *)
%o A086984 (PARI) a(n)=n!+sum(i=2,n,binomial(n-1,n-i)*n*n!)
%Y A086984 Cf. A000407, A086985.
%K A086984 nonn
%O A086984 1,2
%A A086984 _Jon Perry_, Jul 27 2003