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 A223665 #6 Jul 23 2025 04:21:57 %S A223665 11,121,948,6454,44693,321163,2343189,17087771,124218846,901767902, %T A223665 6546694983,47541956223,345294309121,2507850941319,18213891195978, %U A223665 132281285512572,960713718887517,6977351377339193,50674293382202763 %N A223665 Number of nX4 0..1 arrays with rows, diagonals and antidiagonals unimodal. %C A223665 Column 4 of A223669 %H A223665 R. H. Hardin, <a href="/A223665/b223665.txt">Table of n, a(n) for n = 1..210</a> %F A223665 Empirical: a(n) = 9*a(n-1) -8*a(n-2) -63*a(n-3) +250*a(n-4) -152*a(n-5) -522*a(n-6) -2735*a(n-7) +4120*a(n-8) +9651*a(n-9) +1347*a(n-10) -13682*a(n-11) -24899*a(n-12) +6443*a(n-13) +11258*a(n-14) +8578*a(n-15) -11567*a(n-16) +8480*a(n-17) +22660*a(n-18) -17587*a(n-19) +2236*a(n-20) +4536*a(n-21) -2700*a(n-22) -864*a(n-23) %e A223665 Some solutions for n=4 %e A223665 ..0..0..0..1....0..1..1..1....0..1..0..0....0..1..0..0....0..1..1..0 %e A223665 ..1..1..1..0....0..1..1..1....0..1..0..0....0..1..0..0....0..1..1..0 %e A223665 ..1..1..0..0....0..1..1..0....1..0..0..0....0..1..0..0....1..1..1..1 %e A223665 ..0..0..1..0....0..0..0..0....0..1..0..0....0..0..1..0....1..1..1..1 %K A223665 nonn %O A223665 1,1 %A A223665 _R. H. Hardin_ Mar 25 2013