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 A202809 #7 Jun 02 2025 07:28:37 %S A202809 1,15,356,8232,146300,1874539,17870566,133496644,817995997,4261304129, %T A202809 19398449839,78815353079,290571063342,984899160732,3101890356933, %U A202809 9156259810369,25514373644936,67521447453170,170570662562363 %N A202809 Number of nX5 nonnegative integer arrays with each row and column increasing from zero by 0, 1 or 2. %C A202809 Column 5 of A202812 %H A202809 R. H. Hardin, <a href="/A202809/b202809.txt">Table of n, a(n) for n = 1..210</a> %F A202809 Empirical: a(n) = (107411/608225502044160000)*n^20 + (107411/8688935743488000)*n^19 + (292049/711374856192000)*n^18 + (4388269/533531142144000)*n^17 + (17087621/156920924160000)*n^16 + (30492463/31384184832000)*n^15 + (153451759/26900729856000)*n^14 + (33671947/1681295616000)*n^13 + (151751213/4389396480000)*n^12 + (341775353/4828336128000)*n^11 + (8743193411/9656672256000)*n^10 + (10646538107/2414168064000)*n^9 + (5850968901581/941525544960000)*n^8 - (13679248369/3362591232000)*n^7 + (193043821457/3923023104000)*n^6 + (103097176421/653837184000)*n^5 - (5199936999869/37050773760000)*n^4 + (12260594911/61751289600)*n^3 + (692087587/1185125760)*n^2 + (33368033/232792560)*n %e A202809 Some solutions for n=4 %e A202809 ..0..0..0..0..0....0..0..0..0..0....0..0..0..0..0....0..0..0..0..0 %e A202809 ..0..0..0..1..1....0..0..1..2..2....0..0..0..2..2....0..0..1..2..2 %e A202809 ..0..0..1..2..2....0..0..2..2..2....0..0..0..2..4....0..1..1..3..3 %e A202809 ..0..0..1..2..3....0..1..3..4..4....0..1..2..3..4....0..1..2..4..4 %K A202809 nonn %O A202809 1,2 %A A202809 _R. H. Hardin_ Dec 24 2011