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 A201697 #7 Jul 22 2025 16:19:04 %S A201697 3,37,989,35390,930564,14268351,142436489,1034563890,5898023820, %T A201697 27803725006,112491133042,401503571755,1290797861479,3798580774670, %U A201697 10363168825912,26478119492263,63883865534377,146539437113683 %N A201697 Number of nX5 0..2 arrays with rows and columns lexicographically nondecreasing read forwards and nonincreasing read backwards. %C A201697 Column 5 of A201700 %H A201697 R. H. Hardin, <a href="/A201697/b201697.txt">Table of n, a(n) for n = 1..210</a> %F A201697 Empirical: a(n) = (39619/523069747200)*n^16 + (4468181/653837184000)*n^15 + (29013757/130767436800)*n^14 + (1283689/849139200)*n^13 - (51508993/2874009600)*n^12 - (43603801/256608000)*n^11 + (2874162577/914457600)*n^10 - (7499289487/457228800)*n^9 + (16169769137/731566080)*n^8 + (30409918103/653184000)*n^7 + (408990763441/718502400)*n^6 - (175356370649/25660800)*n^5 + (317152595889599/10897286400)*n^4 - (27799492117129/412776000)*n^3 + (2720484273811/30270240)*n^2 - (23317530409/360360)*n + 19289 %e A201697 Some solutions for n=3 %e A201697 ..0..1..1..1..2....0..0..1..1..2....0..0..0..0..1....1..1..1..2..2 %e A201697 ..2..0..0..2..1....0..0..2..2..1....0..1..1..1..0....1..2..2..1..1 %e A201697 ..2..2..2..0..0....2..2..0..0..0....2..0..0..0..0....2..1..1..0..0 %K A201697 nonn %O A201697 1,1 %A A201697 _R. H. Hardin_ Dec 03 2011