A322487 - OEIS

%I #17 Dec 05 2022 06:26:06

%S 1,3,31,686,27036,1688360,154703688,19692332568,3342458334775,

%T 732812082630803,202322386045180686,68898094282978653925,

%U 28443422251718020038049,14029033632468285836567998,8164217197799501761637725983,5545466507405459243366712102466

%N Number of (3*n) X n matrices with nonnegative integer entries and each column sum being 3 up to permutation of rows.

%C Also number of multiset partitions of [1,1,1,2,2,2,...,n,n,n] into nonempty multisets. - _Marko Riedel_, Nov 29 2022

%H Andrew Howroyd, <a href="/A322487/b322487.txt">Table of n, a(n) for n = 0..100</a>

%e a(1) = 3 because up to permutations of rows there are 3 column vectors with sum 3: [1, 1, 1], [2, 1, 0] and [3, 0, 0].

%Y Row n=3 of A219727.

%Y Cf. A165434, A358721.

%K nonn

%O 0,2

%A _Andrew Howroyd_, Dec 11 2018