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 A268416 #25 Sep 11 2024 10:05:56
%S A268416 1,4,35,1280,262292,205515653,592830103236
%N A268416 Number of aligned free polyominoes that will fit in a square of size n X n.
%C A268416 a(n) is the number of free polyominoes that have both width and height <= n. Compare this to _Craig Knecht_'s A268311 which has both height and width = n. The word "aligned" in the title refers to the restriction that the polyominoes have edges parallel to the sides of the square, in contrast with A268427.
%F A268416 a(n) = Sum_{i=1..n*(n+1)/2} A268371(i). - _John Mason_, Sep 11 2024
%Y A268416 Cf. A268311, A268371, A268427.
%K A268416 nonn,more
%O A268416 1,2
%A A268416 _John Mason_, Feb 04 2016
%E A268416 a(6) from _Talmon Silver_, Jul 29 2020
%E A268416 a(7) from _John Mason_, Sep 11 2024