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 A255907 #8 Mar 11 2015 19:13:50
%S A255907 1,2,23,492,15800,693667,39371078,2780643510,237625842970,
%T A255907 24048952078889,2833749745048664,383425910861623475,
%U A255907 58894162142705623291,10170230140575830362828,1958227054977871232165423,417406876191416533261184253,97882032782014459518083172751
%N A255907 Number of collections of nonempty multisets with a total of 2n objects of exactly n colors.
%H A255907 Alois P. Heinz, <a href="/A255907/b255907.txt">Table of n, a(n) for n = 0..200</a>
%F A255907 a(n) = A255903(2n,n).
%e A255907 a(0) = 1: {}.
%e A255907 a(1) = 2: {{1},{1}}, {{1,1}}.
%e A255907 a(2) = 23: {{1},{1},{1},{2}}, {{1},{1},{2},{2}}, {{1},{2},{2},{2}}, {{1},{1},{1,2}}, {{1},{1},{2,2}}, {{1},{2},{1,1}}, {{1},{2},{1,2}}, {{1},{2},{2,2}}, {{2},{2},{1,1}}, {{2},{2},{1,2}}, {{1,1},{1,2}}, {{1,1},{2,2}}, {{1,2},{1,2}}, {{1,2},{2,2}}, {{1},{1,1,2}}, {{1},{1,2,2}}, {{1},{2,2,2}}, {{2},{1,1,1}}, {{2},{1,1,2}}, {{2},{1,2,2}}, {{1,1,1,2}}, {{1,1,2,2}}, {{1,2,2,2}}.
%Y A255907 Cf. A255903.
%K A255907 nonn
%O A255907 0,2
%A A255907 _Alois P. Heinz_, Mar 10 2015