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 A387003 #7 Aug 15 2025 15:58:52
%S A387003 1,1,2,2,9,12,5,54,95,103
%N A387003 Triangle read by rows: T(n,d) is the number of free (d,2)-polyominoids of size n, 2 <= d <= n+1.
%C A387003 If d > n+1, there are T(n,n+1) such polyominoids. The triangle only includes the values for d <= n+1.
%H A387003 Wikipedia, <a href="https://en.wikipedia.org/wiki/Polyominoid">Polyominoid</a>.
%H A387003 <a href="/index/Pol#polyominoes">Index entries for sequences related to polyominoes</a>.
%F A387003 T(n,d) = Sum_{k=1..d} A387004(n,k).
%e A387003 Triangle begins:
%e A387003 n\d| 2 3 4 5
%e A387003 ---+------------
%e A387003 1 | 1
%e A387003 2 | 1 2
%e A387003 3 | 2 9 12
%e A387003 4 | 5 54 95 103
%Y A387003 Columns: A000105 (d=2), A075679 (d=3), A366334 (d=4).
%Y A387003 Cf. A330891 (polyominoes), A385583 (polysticks), A385715 (fixed), A387002, A387004, A387005 (main diagonal).
%K A387003 nonn,tabl,more
%O A387003 1,3
%A A387003 _Pontus von Brömssen_, Aug 14 2025