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 A223995 #6 Jul 23 2025 04:47:58 %S A223995 15,155,1144,7927,55333,388598,2743444,19437479,138010718,981047716, %T A223995 6977843175,49645292212,353262192994,2513898151334,17890175634324, %U A223995 127318180862693,906089796193803,6448444001034017,45892351529878911 %N A223995 Number of nX4 0..2 arrays with antidiagonals unimodal and rows and diagonals nondecreasing. %C A223995 Column 4 of A223999 %H A223995 R. H. Hardin, <a href="/A223995/b223995.txt">Table of n, a(n) for n = 1..210</a> %F A223995 Empirical: a(n) = 15*a(n-1) -69*a(n-2) +66*a(n-3) +226*a(n-4) -172*a(n-5) -1192*a(n-6) +2157*a(n-7) -1714*a(n-8) -2876*a(n-9) +4966*a(n-10) +12095*a(n-11) -17584*a(n-12) +28968*a(n-13) +156*a(n-14) -2874*a(n-15) -2964*a(n-16) +15876*a(n-17) +1008*a(n-18) for n>19 %e A223995 Some solutions for n=3 %e A223995 ..0..0..2..2....0..1..1..1....0..0..0..0....0..0..1..1....0..1..1..2 %e A223995 ..0..1..1..2....1..1..1..2....0..0..2..2....0..0..2..2....0..0..1..2 %e A223995 ..1..1..1..1....0..2..2..2....1..1..1..2....0..2..2..2....0..0..1..1 %K A223995 nonn %O A223995 1,1 %A A223995 _R. H. Hardin_ Mar 30 2013