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 A200155 #14 Mar 02 2018 14:13:48 %S A200155 4,9,22,41,66,107,158,219,304,403,516,661,824,1005,1226,1469,1734, %T A200155 2047,2386,2751,3172,3623,4104,4649,5228,5841,6526,7249,8010,8851, %U A200155 9734,10659,11672,12731,13836,15037,16288,17589,18994,20453,21966,23591,25274,27015 %N A200155 Number of 0..n arrays x(0..3) of 4 elements with zero 3rd differences. %C A200155 Row 4 of A200154. %H A200155 R. H. Hardin, <a href="/A200155/b200155.txt">Table of n, a(n) for n = 1..200</a> %F A200155 Empirical: a(n) = 2*a(n-1) - a(n-2) + 2*a(n-3) - 4*a(n-4) + 2*a(n-5) - a(n-6) + 2*a(n-7) - a(n-8). %F A200155 Empirical g.f.: x*(4 + x + 8*x^2 - 2*x^3 + 4*x^4 + 2*x^6 - x^7) / ((1 - x)^4*(1 + x + x^2)^2). - _Colin Barker_, Mar 02 2018 %e A200155 Some solutions for n=6: %e A200155 ..3....4....2....0....0....4....4....3....3....3....2....2....6....3....5....3 %e A200155 ..3....4....6....4....1....1....5....1....0....0....2....2....1....4....1....4 %e A200155 ..4....3....6....6....3....0....4....1....0....1....3....2....1....4....0....3 %e A200155 ..6....1....2....6....6....1....1....3....3....6....5....2....6....3....2....0 %Y A200155 Cf. A200154. %K A200155 nonn %O A200155 1,1 %A A200155 _R. H. Hardin_, Nov 13 2011