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 A223982 #8 Aug 25 2018 16:15:50 %S A223982 50,684,5029,25410,99634,325120,922768,2346883,5462600,11818092, %T A223982 24045385,46430852,85704412,152105120,260790200,433664645,701719286, %U A223982 1107976716,1711156645,2590185158,3849685950,5626605920,8098142520,11491155975 %N A223982 Number of n X 3 0..3 arrays with rows unimodal and columns nondecreasing. %C A223982 Column 3 of A223987. %H A223982 R. H. Hardin, <a href="/A223982/b223982.txt">Table of n, a(n) for n = 1..210</a> %F A223982 Empirical: a(n) = (353/181440)*n^9 + (5/126)*n^8 + (10571/30240)*n^7 + (251/144)*n^6 + (46793/8640)*n^5 + (1565/144)*n^4 + (159679/11340)*n^3 + (715/63)*n^2 + (6491/1260)*n + 1. %F A223982 Conjectures from _Colin Barker_, Aug 25 2018: (Start) %F A223982 G.f.: x*(50 + 184*x + 439*x^2 - 100*x^3 + 259*x^4 - 210*x^5 + 120*x^6 - 45*x^7 + 10*x^8 - x^9) / (1 - x)^10. %F A223982 a(n) = 10*a(n-1) - 45*a(n-2) + 120*a(n-3) - 210*a(n-4) + 252*a(n-5) - 210*a(n-6) + 120*a(n-7) - 45*a(n-8) + 10*a(n-9) - a(n-10) for n>10. %F A223982 (End) %e A223982 Some solutions for n=3: %e A223982 ..0..2..1....0..3..0....0..1..0....2..2..0....0..1..0....1..2..0....0..0..0 %e A223982 ..0..3..1....0..3..1....2..2..0....3..2..0....0..1..2....2..2..1....0..1..0 %e A223982 ..0..3..1....0..3..1....2..3..2....3..2..2....2..2..3....2..3..3....0..2..1 %Y A223982 Cf. A223987. %K A223982 nonn %O A223982 1,1 %A A223982 _R. H. Hardin_, Mar 30 2013