A084873 - OEIS

%I #13 Oct 08 2017 18:06:27

%S 1,2,9,73,1212,44667,3251186,345094227,39552733796,4234657495267,

%T 409948262617398,36190736880911571,2964860272283578040,

%U 229165985114590010307,16940021231116707830570

%N Number of 6-multiantichains of an n-set.

%H G. C. Greubel, <a href="/A084873/b084873.txt">Table of n, a(n) for n = 0..550</a>

%H Goran Kilibarda and Vladeta Jovovic, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL7/Kilibarda/kili2.html">Antichains of Multisets</a>, J. Integer Seqs., Vol. 7, 2004.

%F a(n) = (1/6!)*(64^n - 30*48^n + 120*40^n + 60*36^n + 60*34^n - 12*33^n - 315*32^n - 720*30^n + 810*28^n + 120*27^n + 480*26^n + 360*25^n - 1080*24^n - 720*23^n - 240*22^n -  540*21^n + 3180*20^n + 750*19^n + 660*18^n + 90*17^n - 4535*16^n - 5420*15^n + 6750*14^n + 5400*13^n - 13620*12^n + 900*11^n + 16440*10^n + 2740*9^n - 12165*8^n + 4110*7^n - 25650*6^n + 25650*5^n + 10474*4^n - 20948*3^n + 7560*2^n).

%t Table[(1/6!)*(64^n - 30*48^n + 120*40^n + 60*36^n + 60*34^n - 12*33^n - 315*32^n - 720*30^n + 810*28^n + 120*27^n + 480*26^n + 360*25^n - 1080*24^n - 720*23^n - 240*22^n - 540*21^n + 3180*20^n + 750*19^n + 660*18^n + 90*17^n - 4535*16^n - 5420*15^n + 6750*14^n + 5400*13^n - 13620*12^n + 900*11^n + 16440*10^n + 2740*9^n - 12165*8^n + 4110*7^n - 25650*6^n + 25650*5^n + 10474*4^n - 20948*3^n + 7560*2^n), {n, 0, 50}] (* _G. C. Greubel_, Oct 08 2017 *)

%Y Cf. A016269, A047707, A051112-A051118, A084869-A084883.

%K nonn

%O 0,2

%A Goran Kilibarda, _Vladeta Jovovic_, Jun 10 2003