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 A335573 #22 Dec 07 2023 14:53:48
%S A335573 1,1,2,4,2,8,1,4,4,2,8,4,4,8,8,8,4,4,8,4,1,2,4,8,8,8,2,8,8,8,8,8,4,8,
%T A335573 4,8,8,8,8,4,4,8,4,8,8,8,4,4,4,4,8,8,4,8,4,4,2,8,8,8,8,8,8,8,8,8,8,4,
%U A335573 4,8,2,8,8,8,8,8,4,4,8,4,8,8,8,8,8,8,8
%N A335573 a(n) is the number of fixed polyominoes corresponding to the free polyomino represented by A246521(n).
%C A335573 Each free polyomino represented by a number in A246521 may correspond to 1, 2, 4 or 8 different fixed polyominoes, generated by rotation or reflection.
%C A335573 In the sequence A246521, the size n polyominoes start at position j = 1 + Sum_{i=0..n-1} A000105(i) and end at position k = Sum_{i=0..n} A000105(i). Therefore, the number of fixed polyominoes, A001168(n), is equal to Sum_{i=j..k} a(i).
%H A335573 Pontus von Brömssen, <a href="/A335573/b335573.txt">Table of n, a(n) for n = 1..6474</a> (polyominoes with up to 10 cells).
%e A335573 The size 4 L-shaped polyomino represented by A246521(6) will generate 8 fixed polyominoes.
%Y A335573 Cf. A000105 (number of free polyominoes of size n).
%Y A335573 Cf. A001168 (number of fixed polyominoes of size n).
%Y A335573 Cf. A246521 (list of free polyominoes in binary coding).
%K A335573 nonn
%O A335573 1,3
%A A335573 _John Mason_, Jan 26 2021