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 A227163 #9 Jul 23 2025 05:34:39 %S A227163 5,36,193,944,4528,20336,85018,330949,1200425,4071133,12971110, %T A227163 39024425,111413038,303209049,789787118,1975994532,4763501990, %U A227163 11094968344,25028901331,54804425836,116706101674,242125356042,490174804573 %N A227163 Number of nX4 0,1 arrays indicating 2X2 subblocks of some larger (n+1)X5 binary array having a sum of one or less, with rows and columns of the latter in lexicographically nondecreasing order. %C A227163 Column 4 of A227165 %H A227163 R. H. Hardin, <a href="/A227163/b227163.txt">Table of n, a(n) for n = 1..210</a> %F A227163 Empirical: a(n) = (1/1689515283456000)*n^19 + (1/42682491371520)*n^18 + (47/118562476032000)*n^17 + (289/10461394944000)*n^16 + (479/5230697472000)*n^15 + (7897/2092278988800)*n^14 + (1632263/10461394944000)*n^13 - (908693/603542016000)*n^12 + (896531/18289152000)*n^11 - (23306879/29262643200)*n^10 + (26023484833/1609445376000)*n^9 - (186161720861/804722688000)*n^8 + (2050542947543/871782912000)*n^7 - (5863470751207/392302310400)*n^6 + (78462384223117/1307674368000)*n^5 - (49466529613783/217945728000)*n^4 + (52739410297759/30875644800)*n^3 - (18770426920009/1715313600)*n^2 + (74837531735/2116296)*n - 43518 for n>8 %e A227163 Some solutions for n=4 %e A227163 ..1..0..0..0....1..1..1..1....1..1..0..0....1..1..1..1....1..1..1..0 %e A227163 ..0..0..0..1....1..1..1..0....1..1..0..0....1..0..0..0....1..1..0..1 %e A227163 ..0..0..1..1....0..0..0..0....0..0..1..0....0..0..0..0....1..0..0..1 %e A227163 ..0..0..0..1....0..0..0..1....0..0..0..0....0..1..1..1....0..0..1..0 %K A227163 nonn %O A227163 1,1 %A A227163 _R. H. Hardin_ Jul 03 2013