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 A229427 #6 Jul 23 2025 05:44:27 %S A229427 30,282,2187,13345,66503,281016,1037193,3420692,10260128,28379127, %T A229427 73192023,177601008,408454945,895812869,1883191437,3811219431, %U A229427 7453126082,14128822736,26035706883,46749593643,81969420795,140605855270 %N A229427 Number of nX7 0..2 arrays with horizontal differences mod 3 never 1, vertical differences mod 3 never -1, rows lexicographically nondecreasing, and columns lexicographically nonincreasing. %C A229427 Column 7 of A229428 %H A229427 R. H. Hardin, <a href="/A229427/b229427.txt">Table of n, a(n) for n = 1..210</a> %F A229427 Empirical: a(n) = (1/660441600)*n^14 + (1/9434880)*n^13 + (1/311850)*n^12 + (283/4989600)*n^11 + (23/34560)*n^10 + (5/896)*n^9 + (55843/1587600)*n^8 + (154153/907200)*n^7 + (4503127/7257600)*n^6 + (1244953/725760)*n^5 + (56059/14400)*n^4 + (1646347/302400)*n^3 + (401116003/50450400)*n^2 + (124079/24024)*n + 5 %e A229427 Some solutions for n=4 %e A229427 ..1..1..0..0..0..0..0....1..1..1..1..0..0..0....1..1..0..0..0..0..0 %e A229427 ..1..1..0..0..0..0..0....2..1..1..1..0..0..0....1..1..1..1..0..0..0 %e A229427 ..1..1..0..0..0..0..0....2..2..2..1..1..0..0....2..2..1..1..1..1..1 %e A229427 ..1..1..0..0..0..0..0....2..2..2..1..1..0..0....2..2..2..2..2..2..1 %K A229427 nonn %O A229427 1,1 %A A229427 _R. H. Hardin_ Sep 22 2013