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 A377593 #6 Nov 02 2024 14:36:52
%S A377593 1,8,151,9472,2081051,1643823600,4742607132499,50303895480064088,
%T A377593 1966122506151835674303,283294196554063138439927568,
%U A377593 150432366492029200690537003170367,294212995394376069103067524948055548348,2117957146063247996594586658579155551318256103,56084287855193446153928896349599388059636859288133588,5460061052459125116800111315595463810654508452342242195388707
%N A377593 Number of aligned fixed polyominoes that will fit in a square of size n X n.
%C A377593 a(n) is the number of fixed polyominoes that have both width and height <= n. The word "aligned" in the title refers to the restriction that the polyominoes have edges parallel to the sides of the square.
%F A377593 a(n) = Sum_{i=1..n,j=1..n} A292357(i,j).
%e A377593 a(2) = 8 because of the monomino, 2 alignments of the domino, 4 alignments of the L-shaped tromino, and the square tetromino.
%Y A377593 Cf. A292357, A268416, A268404.
%K A377593 nonn
%O A377593 1,2
%A A377593 _John Mason_, Nov 02 2024