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 A223977 #6 Jul 23 2025 04:44:35 %S A223977 81,6561,186004,2558848,22935921,153196498,822895397,3731866676, %T A223977 14772553616,52279545002,168389072033,500454038667,1387317570171, %U A223977 3618413260028,8942729611918,21066089007345,47533740360251 %N A223977 Number of 4Xn 0..2 arrays with rows and antidiagonals unimodal. %C A223977 Row 4 of A223975 %H A223977 R. H. Hardin, <a href="/A223977/b223977.txt">Table of n, a(n) for n = 1..210</a> %F A223977 Empirical: a(n) = (456419/5230697472000)*n^16 + (35741/12108096000)*n^15 + (4696759/65383718400)*n^14 + (1960073/1779148800)*n^13 + (31966559/2612736000)*n^12 + (461185847/4790016000)*n^11 + (496257731/914457600)*n^10 + (445395499/203212800)*n^9 + (228272848649/36578304000)*n^8 + (5589292243/435456000)*n^7 + (282633985/14370048)*n^6 + (3122820053/239500800)*n^5 - (91030209653/108972864000)*n^4 - (327561926401/4540536000)*n^3 + (185306939/3439800)*n^2 + (13865993/360360)*n + 7 %e A223977 Some solutions for n=3 %e A223977 ..1..0..0....0..0..0....1..1..0....0..1..0....0..0..2....0..2..1....0..2..0 %e A223977 ..2..2..1....1..2..2....1..2..0....2..1..0....1..1..2....0..2..0....0..1..1 %e A223977 ..1..1..1....1..2..2....1..1..0....0..1..1....1..0..0....0..0..0....2..2..1 %e A223977 ..0..1..0....2..1..0....0..2..0....0..1..0....0..2..1....0..2..0....0..0..2 %K A223977 nonn %O A223977 1,1 %A A223977 _R. H. Hardin_ Mar 30 2013