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 A188976 #8 Jul 22 2025 11:30:03 %S A188976 1,9,116,900,7836,71865,640513,5706113,51056136,456396688,4078122040, %T A188976 36448590305,325763780945,2911451082361,26020738951500, %U A188976 232557947597540,2078461123504804,18576017680577225,166021162669244641 %N A188976 Number of nX2 array permutations with each element moved but moved no more than a city block distance of two. %C A188976 Column 2 of A188981 %H A188976 R. H. Hardin, <a href="/A188976/b188976.txt">Table of n, a(n) for n = 1..200</a> %F A188976 Empirical: a(n) = 8*a(n-1) +3*a(n-2) +68*a(n-3) -142*a(n-4) -354*a(n-5) +225*a(n-6) +430*a(n-7) +47*a(n-8) +308*a(n-9) -16*a(n-10) -932*a(n-11) +281*a(n-12) +24*a(n-13) -195*a(n-14) +112*a(n-15) +22*a(n-16) +22*a(n-17) -a(n-18) -6*a(n-19) +a(n-20) %e A188976 Some solutions for 3X2 %e A188976 ..1..5....1..0....2..5....2..3....2..0....3..5....1..0....2..3....4..0....4..0 %e A188976 ..4..2....3..5....1..0....5..4....5..1....1..2....5..4....0..1....1..2....1..5 %e A188976 ..0..3....2..4....3..4....0..1....3..4....0..4....3..2....5..4....5..3....3..2 %K A188976 nonn %O A188976 1,2 %A A188976 _R. H. Hardin_ Apr 14 2011