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 A229797 #6 Jul 23 2025 05:47:25 %S A229797 650,250841,21907055,733861607,13111482259,150943642765,1257194266246, %T A229797 8170451731089,43642376268844,198859490805437,794550500198885, %U A229797 2842727725991231,9257049674121653,27794351169785161,77754305616698860 %N A229797 Number of 4X4 0..n arrays with rows and columns in lexicographically nondecreasing order. %C A229797 Row 4 of A229794 %H A229797 R. H. Hardin, <a href="/A229797/b229797.txt">Table of n, a(n) for n = 1..41</a> %F A229797 Empirical: a(n) = (1/252)*n^16 + (17/252)*n^15 + (1349/2520)*n^14 + (26531/10080)*n^13 + (2597/288)*n^12 + (691/30)*n^11 + (694109/15120)*n^10 + (2229581/30240)*n^9 + (5469/56)*n^8 + (546263/5040)*n^7 + (73249/720)*n^6 + (7297/90)*n^5 + (47305/864)*n^4 + (16739/540)*n^3 + (36263/2520)*n^2 + (533/105)*n + 1 %e A229797 Some solutions for n=2 %e A229797 ..0..0..0..0....0..0..1..2....0..0..1..2....0..0..0..2....0..0..0..1 %e A229797 ..0..0..0..1....0..0..2..0....0..1..1..2....0..1..2..2....0..1..2..1 %e A229797 ..0..2..2..1....1..2..2..1....1..0..1..2....0..2..1..2....1..0..1..2 %e A229797 ..1..0..1..0....2..1..2..1....2..0..1..2....2..2..2..2....2..0..0..0 %K A229797 nonn %O A229797 1,1 %A A229797 _R. H. Hardin_, Sep 29 2013