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 A181202 #5 Jun 02 2025 03:13:03 %S A181202 0,168,16632,1729728,199536480,25241364720,3445446284280, %T A181202 500598983364480,76591644454765440,12237255920840932800, %U A181202 2028351316862121451200,346968438887939861076480,60995474427232155123331200 %N A181202 a(n)=0!*1!*2!*3!*(4*n)!*6*n*(n-1) / ((n)!*(n+1)!*(n+2)!*(n+3)!). %C A181202 (Empirical) Number of nX4 matrices containing a defective permutation of 1..4*n in strictly increasing order rowwise and columnwise, with one permutation value omitted and one repeated (see example) %C A181202 Column 4 of A181204 %H A181202 R. H. Hardin, <a href="/A181202/b181202.txt">Table of n, a(n) for n=1..50</a> %e A181202 Some solutions for 2X4 %e A181202 ..1..3..4..5....1..2..4..5....2..4..5..7....1..2..3..4....1..3..4..6 %e A181202 ..2..5..7..8....3..5..7..8....3..6..7..8....4..5..6..8....5..6..7..8 %K A181202 nonn %O A181202 1,2 %A A181202 _R. H. Hardin_ Oct 10 2010