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 A212235 #6 Jun 02 2025 07:56:11 %S A212235 31,311,2902,26637,242780,2204646,19976155,180744711,1633768428, %T A212235 14757208260,133224377745,1202213897088,10845157390965,97807813761227, %U A212235 881892198839574,7950191559259765,71659250039164212,645816864760873772 %N A212235 Number of 0..2 arrays of length 2+2*n with sum no more than 2*n in any length 2n subsequence (=50% duty cycle). %C A212235 Row 3 of A212232 %H A212235 R. H. Hardin, <a href="/A212235/b212235.txt">Table of n, a(n) for n = 1..210</a> %e A212235 Some solutions for n=3 %e A212235 ..0....0....1....0....0....1....1....0....2....1....1....2....2....0....0....1 %e A212235 ..0....1....0....1....1....0....1....2....2....0....1....1....0....2....0....1 %e A212235 ..0....0....0....1....1....1....0....1....1....0....0....0....0....1....0....2 %e A212235 ..0....1....0....0....1....0....0....0....0....0....0....0....0....0....2....0 %e A212235 ..0....0....1....1....1....2....2....1....0....0....2....1....0....0....0....2 %e A212235 ..0....1....1....0....2....0....1....1....0....0....1....0....1....0....2....0 %e A212235 ..0....2....2....0....0....0....1....1....1....1....2....0....1....0....1....0 %e A212235 ..1....1....1....1....1....0....2....1....2....2....1....2....0....0....1....1 %K A212235 nonn %O A212235 1,1 %A A212235 _R. H. Hardin_ May 06 2012