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 A308389 #10 May 24 2019 17:34:02
%S A308389 1,0,15,2380,1056496,1006985994,1762986495425,5113595093793395,
%T A308389 22839265373518360690,148735602883834110187329,
%U A308389 1353820891564948063221216616,16652183007514287292261315076600,269267286009015985660399792630965620,5594310615550213586375706097295466365365
%N A308389 a(n) = (1/n!) * Sum_{i_1=1..4} Sum_{i_2=1..4} ... Sum_{i_n=1..4} (-1)^(i_1 + i_2 + ... + i_n) * multinomial(i_1 + i_2 + ... + i_n; i_1, i_2, ..., i_n).
%o A308389 (PARI) {a(n) = sum(i=n, 4*n, (-1)^i*i!*polcoef(sum(j=1, 4, x^j/j!)^n, i))/n!}
%Y A308389 Row n=4 of A308356.
%Y A308389 Cf. A144508.
%K A308389 nonn
%O A308389 0,3
%A A308389 _Seiichi Manyama_, May 23 2019