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 A229871 #6 Jul 23 2025 05:48:25 %S A229871 2432,384183,15106048,266515625,2805425280,20610104767,116211580928, %T A229871 535021318017,2098414000000,7227967108439,22362655260672, %U A229871 63219695614153,165498794685056,405459218109375,937601561264128,2060839403682497 %N A229871 Number of 4X4 0..n arrays with corresponding row and column sums equal. %C A229871 Row 4 of A229870 %H A229871 R. H. Hardin, <a href="/A229871/b229871.txt">Table of n, a(n) for n = 1..73</a> %F A229871 Empirical: a(n) = (29/140)*n^13 + (377/140)*n^12 + (3449/210)*n^11 + (13057/210)*n^10 + (34249/210)*n^9 + (21941/70)*n^8 + (6826/15)*n^7 + (53206/105)*n^6 + (60773/140)*n^5 + (119003/420)*n^4 + (28807/210)*n^3 + (9791/210)*n^2 + (348/35)*n + 1 %e A229871 Some solutions for n=4 %e A229871 ..0..0..0..0....0..0..0..1....0..0..0..1....0..0..1..1....0..0..1..1 %e A229871 ..0..1..2..3....0..0..4..2....0..1..1..3....0..1..2..1....0..1..0..2 %e A229871 ..0..4..0..0....1..4..0..1....1..4..2..0....1..3..4..3....1..2..0..0 %e A229871 ..0..1..2..3....0..2..2..3....0..0..4..3....1..0..4..1....1..0..2..0 %K A229871 nonn %O A229871 1,1 %A A229871 _R. H. Hardin_, Oct 01 2013