A062817 a(n) = Sum_{i=0..n} i^(n - i)*(n - i)^i.

0, 1, 4, 22, 152, 1251, 11980, 130908, 1607488, 21915525, 328477396, 5368649634, 95026828136, 1810930007495, 36968511612124, 804857864647544, 18615565047797520, 455834881650397833, 11780900281221329892

Offset: 1

Author

Olivier Gérard, Jun 23 2001

Keywords

• nonn
• easy

Links

• G. C. Greubel, Table of n, a(n) for n = 1..425

Crossrefs

Cf. A252708, A252709, A252710.

Programs

Mathematica

Table[Sum[i^(n-i)*(n-i)^i,{i,0,n}],{n,20}] (* Harvey P. Dale, Jan 14 2017 *)

PARI

for(n=1,25, print1(sum(k=0,n, k^(n-k)*(n-k)^k), ", ")) \\ G. C. Greubel, Jan 25 2017

Formula

a(n) ~ sqrt(Pi/3) * n^(n+1/2) / 2^(n+1/2). - Vaclav Kotesovec, Dec 20 2014

Extensions

Prior Mathematica program deleted by Harvey P. Dale, Jan 14 2017