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 A204644 #28 Apr 05 2019 12:23:51 %S A204644 8,16,28,48,80,132,216,352,572,928,1504,2436,3944,6384,10332,16720, %T A204644 27056,43780,70840,114624,185468,300096,485568,785668,1271240,2056912, %U A204644 3328156,5385072,8713232,14098308,22811544,36909856,59721404,96631264,156352672,252983940 %N A204644 Number of (n+1) X 2 0..1 arrays with column and row pair sums b(i,j)=a(i,j)+a(i,j-1) and c(i,j)=a(i,j)+a(i-1,j) nondecreasing in column and row directions, respectively. %H A204644 R. H. Hardin, <a href="/A204644/b204644.txt">Table of n, a(n) for n = 1..210</a> %H A204644 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (2, 0, -1) (empirical). %F A204644 Empirical: a(n) = 2*a(n-1) - a(n-3). %F A204644 From the empirical recurrence, a(n) = 4*(Fibonacci(n + 3) - 1). - _Ehren Metcalfe_, Apr 04 2019 %e A204644 Some solutions for n=5: %e A204644 0 1 0 1 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 0 %e A204644 0 1 0 1 0 0 0 0 1 0 0 1 0 1 0 0 0 0 1 1 %e A204644 1 0 0 1 0 0 0 0 0 1 0 1 1 0 0 1 0 0 1 1 %e A204644 0 1 0 1 0 1 0 0 1 1 0 1 0 1 0 1 0 1 1 1 %e A204644 0 1 1 0 1 0 0 0 1 1 0 1 1 0 0 1 1 1 1 1 %e A204644 1 1 0 1 0 1 0 1 1 1 0 1 0 1 1 1 1 1 1 1 %Y A204644 Column 1 of A204651. %K A204644 nonn %O A204644 1,1 %A A204644 _R. H. Hardin_, Jan 17 2012