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 A062817 #14 Jan 25 2017 18:26:33
%S A062817 0,1,4,22,152,1251,11980,130908,1607488,21915525,328477396,5368649634,
%T A062817 95026828136,1810930007495,36968511612124,804857864647544,
%U A062817 18615565047797520,455834881650397833,11780900281221329892
%N A062817 a(n) = Sum_{i=0..n} i^(n - i)*(n - i)^i.
%H A062817 G. C. Greubel, <a href="/A062817/b062817.txt">Table of n, a(n) for n = 1..425</a>
%F A062817 a(n) ~ sqrt(Pi/3) * n^(n+1/2) / 2^(n+1/2). - _Vaclav Kotesovec_, Dec 20 2014
%t A062817 Table[Sum[i^(n-i)*(n-i)^i,{i,0,n}],{n,20}] (* _Harvey P. Dale_, Jan 14 2017 *)
%o A062817 (PARI) for(n=1,25, print1(sum(k=0,n, k^(n-k)*(n-k)^k), ", ")) \\ _G. C. Greubel_, Jan 25 2017
%Y A062817 Cf. A252708, A252709, A252710.
%K A062817 nonn,easy
%O A062817 1,3
%A A062817 _Olivier Gérard_, Jun 23 2001
%E A062817 Prior Mathematica program deleted by _Harvey P. Dale_, Jan 14 2017