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%I #36 Apr 24 2015 18:37:26
%S 1,1,4,10,25,49,103,184,331,554,911,1424,2204,3278,4817,6896,9746,
%T 13487,18480,24882,33192,43683,56994,73512,94131,119340,150300,187732,
%U 233065,287248,352153,428944,519949,626737,752095,897994,1067924,1264241,1491155,1751672
%N Number of ways to partition the multiset consisting of n copies each of 1, 2, and 3 into n sets of size 3.
%H Alois P. Heinz, <a href="/A254233/b254233.txt">Table of n, a(n) for n = 0..1000</a>
%F G.f.: (x^12-x^11+x^10+3*x^9+5*x^8+x^7+4*x^6+x^5+5*x^4+3*x^3+x^2-x+1) / ((x^2+1)*(x^2-x+1)*(x^2+x+1)^3*(x+1)^4*(x-1)^8). - _Alois P. Heinz_, Apr 21 2015
%e For n = 2, the set {1,1,2,2,3,3} can be partitioned into two sets in four ways: {{112},{233}}, {{113},{223}}, {{122},{133}}, and {{123},{123}}.
%Y Cf. A002135, A254243.
%Y Column k=3 of A257462.
%K nonn,easy
%O 0,3
%A _Tatsuru Murai_, Jan 27 2015
%E Fixed definition and examples by _Kellen Myers_, Apr 21 2015
%E a(14)-a(39) from _Alois P. Heinz_, Apr 21 2015
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