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 A053623 #10 Jan 04 2022 21:03:14
%S A053623 1,2,4,14,38,126,252,1662,7180,39430,111064,803876,2863992,12123360,
%T A053623 24246720,329012784,2602608516
%N A053623 Number of distinct non-extendable sequences (x(1),x(2),...,x(k)) such that each x(i) is in {1,2,...,n} and (x(j) AND x(i)) <> x(j) for i=2..k, j=1..i-1.
%D A053623 Related to Mathematical Recreations, Scientific American, March 2000.
%H A053623 Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a053/A053623.java">Java program</a> (github)
%e A053623 a(3)=4, since the allowable sequences are (1,2), (2,1), (3,1,2), (3,2,1).
%e A053623 (1,3) is not allowed because 1 AND 3 = 01 AND 11 (base 2) = 1.
%e A053623 (3,1) is not allowed because it can be extended to (3,1,2).
%Y A053623 Cf. A054668.
%K A053623 nonn
%O A053623 1,2
%A A053623 _John W. Layman_, Mar 21 2000
%E A053623 a(17) from _Sean A. Irvine_, Jan 04 2022