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 A070307 #12 Jun 13 2025 08:20:09
%S A070307 1,16,1000,160000,52521875,30840979456,29509034655744,
%T A070307 42998169600000000,90647430472564453125,265599227914240000000000,
%U A070307 1047192117300356121695451136,5410240907043328777415185924096,35821862005173382840059779052734375,298285661929377847941529600000000000000
%N A070307 Number of n X n matrices with nonnegative integer entries such that every row sum equals 3.
%H A070307 Indranil Ghosh, <a href="/A070307/b070307.txt">Table of n, a(n) for n = 1..160</a>
%F A070307 a(n) = C(n+2, 3)^n = A000292(n)^n.
%F A070307 a(n) ~ 6^(-n)*exp(3-5/(2*n))*n^(3*n). - _Stefano Spezia_, Jun 13 2025
%t A070307 Table[ Binomial[n + 2, 3]^n, {n, 1, 14}]
%o A070307 (PARI) a(n) = binomial(n+2, 3)^n; \\ _Michel Marcus_, Mar 10 2017
%o A070307 (Python)
%o A070307 import math
%o A070307 f=math.factorial
%o A070307 def C(n, r): return f(n)/ f(r)/ f(n-r)
%o A070307 def A070307(n): return C(n + 2, 3)**n # _Indranil Ghosh_, Mar 10 2017
%Y A070307 Cf. A061718, A000292.
%K A070307 nonn
%O A070307 1,2
%A A070307 Sharon Sela (sharonsela(AT)hotmail.com), May 10 2002
%E A070307 More terms from _Robert G. Wilson v_, May 10 2002
%E A070307 More terms from _Michel Marcus_, Mar 10 2017