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 A227383 #6 Jul 23 2025 05:36:30 %S A227383 5,30,185,1104,6160,31073,141192,581706,2192737,7631150,24723499, %T A227383 75114814,215382006,586096131,1520882101,3779307010,9026380556, %U A227383 20787492011,46293089506,99943655427,209652253128,428180495383 %N A227383 Number of nX4 0,1 arrays indicating 2X2 subblocks of some larger (n+1)X5 binary array having a sum of one, with rows and columns of the latter in lexicographically nondecreasing order. %C A227383 Column 4 of A227385 %H A227383 R. H. Hardin, <a href="/A227383/b227383.txt">Table of n, a(n) for n = 1..210</a> %F A227383 Empirical: a(n) = (1/2534272925184000)*n^19 + (23/800296713216000)*n^18 + (31/29640619008000)*n^17 + (1061/31384184832000)*n^16 + (1/1793792000)*n^15 + (901/89159616000)*n^14 + (573137/7846046208000)*n^13 + (19320181/3621252096000)*n^12 - (25008281/201180672000)*n^11 + (332913253/109734912000)*n^10 - (5757514877/134120448000)*n^9 + (1008987604001/2414168064000)*n^8 - (7198243864451/3923023104000)*n^7 - (144244343741471/11769069312000)*n^6 + (12251347161947/40864824000)*n^5 - (164980284780767/59439744000)*n^4 + (28073158072/1786785)*n^3 - (35127268025713/617512896)*n^2 + (14284038375031/116396280)*n - 121172 for n>7 %e A227383 Some solutions for n=4 %e A227383 ..0..1..0..0....1..0..0..0....0..1..0..0....0..0..1..0....0..1..0..0 %e A227383 ..1..0..1..1....0..1..0..0....0..0..1..1....1..0..0..0....1..0..0..0 %e A227383 ..0..0..1..1....0..0..1..0....0..0..0..1....0..0..0..0....0..1..0..1 %e A227383 ..0..0..1..0....0..0..0..1....0..0..1..1....0..1..1..1....0..1..1..1 %K A227383 nonn %O A227383 1,1 %A A227383 _R. H. Hardin_ Jul 09 2013