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 A250651 #6 Jul 23 2025 12:39:14 %S A250651 120,2870,28238,163043,677505,2225195,6290716,15474251,34620063, %T A250651 71045837,136895633,249167782,432945014,721867127,1163471851, %U A250651 1819556318,2767225673,4114863787,5983678292,8546815362,11983543443,16566644515 %N A250651 Number of length 7+1 0..n arrays with the sum of the maximum of each adjacent pair multiplied by some arrangement of +-1 equal to zero. %C A250651 Row 7 of A250646 %H A250651 R. H. Hardin, <a href="/A250651/b250651.txt">Table of n, a(n) for n = 1..34</a> %e A250651 Some solutions for n=4 %e A250651 ..4....2....3....3....1....4....1....1....2....4....4....1....1....0....0....0 %e A250651 ..0....2....2....1....0....1....0....1....0....0....1....1....2....1....2....0 %e A250651 ..1....3....4....0....1....4....2....0....4....3....4....0....3....4....2....4 %e A250651 ..1....4....4....4....4....0....0....3....2....3....0....2....0....1....1....1 %e A250651 ..1....4....3....4....4....4....1....1....3....0....0....3....1....0....1....0 %e A250651 ..0....0....3....1....2....0....1....3....0....4....0....1....0....0....0....1 %e A250651 ..0....1....3....0....2....2....0....3....2....0....2....2....4....2....3....1 %e A250651 ..0....2....3....1....1....0....4....4....1....3....1....4....2....2....2....1 %K A250651 nonn %O A250651 1,1 %A A250651 _R. H. Hardin_, Nov 26 2014