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 A378169 #8 Dec 03 2024 12:41:31
%S A378169 1,1,2,4,9,18,37,62,86,78,61,34,14,4,1
%N A378169 Number of free polyominoes with n cells with at most 3 collinear cell centers on any line in the plane.
%H A378169 Dave Budd, <a href="https://github.com/daveisagit/collinear-polyominoes/blob/main/src/A378169.py">Exhaustive proof of A378169</a>
%F A378169 a(n) = Sum_{k=1..3} A377942(n,k).
%e A378169 For n=15, the only polyomino is
%e A378169 ###
%e A378169 ###
%e A378169 ###
%e A378169 ## #
%e A378169 ###
%o A378169 (Python) # See link
%Y A378169 Cf. A000105, A377756, A377942.
%K A378169 nonn,fini,full
%O A378169 1,3
%A A378169 _Dave Budd_, Nov 18 2024