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 A183827 #7 Jul 22 2025 09:13:23 %S A183827 1,15,15,225,813,225,3375,43947,43947,3375,50625,2377341,8538066, %T A183827 2377341,50625,759375,128578815,1661285961,1661285961,128578815, %U A183827 759375,11390625,6954559893,323115202755,1163575148283,323115202755,6954559893,11390625 %N A183827 T(n,k)=1/256 the number of (n+1)X(k+1) 0..3 arrays with no 2X2 subblock being a reflection across the shared element pair of any horizontal or vertical neighbor. %C A183827 Table starts %C A183827 ...........1...............15.................225..................3375 %C A183827 ..........15..............813...............43947...............2377341 %C A183827 .........225............43947.............8538066............1661285961 %C A183827 ........3375..........2377341..........1661285961.........1163575148283 %C A183827 .......50625........128578815........323115202755.......814479338538099 %C A183827 ......759375.......6954559893......62851591581012....570213177028325955 %C A183827 ....11390625.....376152548283...12225396762980829.399185865558804067443 %C A183827 ...170859375...20345104031589.2378005715920214025 %C A183827 ..2562890625.1100412240703119 %C A183827 .38443359375 %H A183827 R. H. Hardin, <a href="/A183827/b183827.txt">Table of n, a(n) for n = 1..60</a> %e A183827 Some solutions with upper left block zero for 4X3 %e A183827 ..0..0..0....0..0..3....0..0..2....0..0..2....0..0..0....0..0..1....0..0..1 %e A183827 ..0..0..1....0..0..3....0..0..2....0..0..1....0..0..2....0..0..3....0..0..1 %e A183827 ..1..0..3....1..2..0....0..3..2....2..1..1....2..2..0....2..3..0....1..0..3 %e A183827 ..3..3..0....2..2..2....0..2..3....3..1..1....1..3..3....2..2..1....1..0..0 %Y A183827 Column 1 is A001024(n-1) %K A183827 nonn,tabl %O A183827 1,2 %A A183827 _R. H. Hardin_ Jan 07 2011