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 A069404 #13 Aug 18 2024 23:03:35 %S A069404 7,55,377,2427,15253,94847,587031,3625675,22372413,137993145, %T A069404 850987067,5247512077,32357022035,199515609775,1230218484787, %U A069404 7585536760417,46772417567873,288398549126971,1778263916566525,10964764644841043,67608669872179151,416874624972396255 %N A069404 Half the number of n X 4 binary arrays with a path of adjacent 1's and a path of adjacent 0's from top row to bottom row. %H A069404 Sean A. Irvine, <a href="/A069404/b069404.txt">Table of n, a(n) for n = 1..250</a> %H A069404 Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a069/A069404.java">Java program</a> (github) %Y A069404 Cf. 1 X n A000225, 2 X n A016269, vertical path of 1 A069361-A069395, vertical paths of 0+1 A069396-A069416, vertical path of 1 not 0 A069417-A069428, no vertical paths A069429-A069447, no horizontal or vertical paths A069448-A069452. %K A069404 nonn %O A069404 1,1 %A A069404 _R. H. Hardin_, Mar 22 2002 %E A069404 More terms from _Sean A. Irvine_, Aug 18 2024