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 A223971 #6 Jul 23 2025 04:43:41 %S A223971 46,2116,76092,2558848,84988435,2809740785,92756321858,3060966419662, %T A223971 100999995564503,3332485315028073,109953896394879299, %U A223971 3627869207377692043,119699463417292189730,3949414024096794560292,130308602654739064528903 %N A223971 Number of nX4 0..2 arrays with rows and antidiagonals unimodal. %C A223971 Column 4 of A223975 %H A223971 R. H. Hardin, <a href="/A223971/b223971.txt">Table of n, a(n) for n = 1..210</a> %F A223971 Empirical: a(n) = 46*a(n-1) -475*a(n-2) +1981*a(n-3) -20047*a(n-4) +170659*a(n-5) -619313*a(n-6) +1472430*a(n-7) -5125985*a(n-8) +14966969*a(n-9) -26289219*a(n-10) +49504177*a(n-11) -100448013*a(n-12) +127366991*a(n-13) -120709682*a(n-14) +121925145*a(n-15) -83316868*a(n-16) +21878656*a(n-17) -230400*a(n-18) %e A223971 Some solutions for n=3 %e A223971 ..0..2..2..2....0..2..0..0....2..1..1..1....0..0..2..0....2..2..1..0 %e A223971 ..1..2..1..0....0..2..1..1....1..1..2..2....0..2..1..1....1..1..1..2 %e A223971 ..0..0..0..0....0..0..1..2....0..2..2..2....1..1..2..0....1..0..0..0 %K A223971 nonn %O A223971 1,1 %A A223971 _R. H. Hardin_ Mar 30 2013