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 A223976 #6 Jul 23 2025 04:44:22 %S A223976 27,729,9515,76092,440628,2026448,7829639,26375691,79507149,218578373, %T A223976 555979549,1323191288,2972776392,6350443334,12975277251,25482263325, %U A223976 48302292951,88682057873,158180868607,274824912452,466153399196 %N A223976 Number of 3Xn 0..2 arrays with rows and antidiagonals unimodal. %C A223976 Row 3 of A223975 %H A223976 R. H. Hardin, <a href="/A223976/b223976.txt">Table of n, a(n) for n = 1..210</a> %F A223976 Empirical: a(n) = (5051/239500800)*n^12 + (17911/39916800)*n^11 + (132833/21772800)*n^10 + (35869/725760)*n^9 + (2045741/7257600)*n^8 + (425867/403200)*n^7 + (62493899/21772800)*n^6 + (727483/145152)*n^5 + (33993559/5443200)*n^4 + (2107249/907200)*n^3 + (3822521/831600)*n^2 + (49331/13860)*n + 1 %e A223976 Some solutions for n=3 %e A223976 ..1..2..0....1..2..2....1..2..0....0..1..2....2..0..0....2..2..0....2..0..0 %e A223976 ..1..0..0....0..2..2....2..2..1....0..2..2....1..1..1....0..1..2....2..1..0 %e A223976 ..2..1..0....0..1..1....0..2..2....1..2..2....0..1..1....2..0..0....2..2..1 %K A223976 nonn %O A223976 1,1 %A A223976 _R. H. Hardin_ Mar 30 2013