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 A220580 #6 Jul 23 2025 01:14:55 %S A220580 1,8,21,115,371,1504,5240,19904,71787,266591,973703,3590009,13161398, %T A220580 48409054,177699822,653013280,2398088376,8809799868,32356803616, %U A220580 118855121770,436550962678,1603501078153,5889674104016,21633105877502 %N A220580 Equals one maps: number of 2Xn binary arrays indicating the locations of corresponding elements equal to exactly one of their horizontal and antidiagonal neighbors in a random 0..1 2Xn array. %C A220580 Row 2 of A220579 %H A220580 R. H. Hardin, <a href="/A220580/b220580.txt">Table of n, a(n) for n = 1..210</a> %e A220580 Some solutions for n=3 %e A220580 ..0..0..0....1..0..1....1..1..0....1..0..0....0..1..1....0..0..1....0..0..1 %e A220580 ..0..0..0....1..1..1....0..1..1....0..0..0....1..0..1....1..0..0....1..0..1 %K A220580 nonn %O A220580 1,2 %A A220580 _R. H. Hardin_ Dec 16 2012