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 A383255 #13 Apr 23 2025 14:57:45
%S A383255 1,4,194,107080,672498596,48104236145168,39202958861329453384,
%T A383255 364022757339778569993689888,38513979937284562006371342202842000,
%U A383255 46429021191757554279412904483559912259714112,637737721080296383894709847744103523361428384973270816
%N A383255 Number of n X n {0,1,2,3} matrices having no 1's to the right of any 0's and no 3's above any 2's.
%C A383255 These are matrices with no [0,1] or [3] submatrices.
%C A383255 [2]
%H A383255 John Tyler Rascoe, <a href="/A383255/a383255.py.txt">Python program</a>.
%F A383255 a(n) <= A060757(n).
%e A383255 The 3 X 3 matrices below are counted under a(3) = 107080:
%e A383255 [0,0,0] [1,0,2] [2,3,2]
%e A383255 [0,0,0] [1,0,3] [3,3,3]
%e A383255 [0,0,0],[0,2,3],[3,3,3].
%o A383255 (Python)
%o A383255 # see links
%Y A383255 Cf. A002416, A006506, A014235, A060757, A181213, A213977, A381857.
%K A383255 nonn
%O A383255 0,2
%A A383255 _John Tyler Rascoe_, Apr 20 2025
%E A383255 a(5)-a(10) from _Bert Dobbelaere_, Apr 23 2025