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 A143544 #11 Nov 01 2021 00:43:26
%S A143544 1,2,2,2,2,2,1,1,1,1,2,2,2,2,2,1,1,1,1,1,1,2,2,2,2,2,2,2,1,1,1,1,1,1,
%T A143544 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,2,2,2
%N A143544 Triangle read by rows, T(n,k) = 2 if n is prime, 1 otherwise; 1<=k<=n.
%C A143544 Row sums = A143545: (1, 4, 6, 4, 10, 6, 14,...) = componentwise addition of (1, 2, 3, 4, 5,...) and A061397: (0, 2, 3, 0, 5, 0, 7,...).
%H A143544 Michael De Vlieger, <a href="/A143544/b143544.txt">Table of n, a(n) for n = 1..11325</a>
%F A143544 Triangle read by rows, T(n,k) = 2 if n is prime, 1 otherwise; 1<=k<=n.
%F A143544 T(n, k) = A143536(n, k) + 1. - _Georg Fischer_, Oct 31 2021
%e A143544 First few rows of the triangle =
%e A143544 1;
%e A143544 2, 2;
%e A143544 2, 2, 2;
%e A143544 1, 1, 1, 1;
%e A143544 2, 2, 2, 2, 2;
%e A143544 1, 1, 1, 1, 1, 1;
%e A143544 2, 2, 2, 2, 2, 2, 2;
%e A143544 ...
%t A143544 Table[1 + Boole[PrimeQ[n]], {n, 11}, {k, n}] // Flatten (* _Michael De Vlieger_, Oct 31 2021 *)
%Y A143544 Cf. A010051, A061397, A143536, A143545.
%K A143544 nonn,tabl
%O A143544 1,2
%A A143544 _Gary W. Adamson_, Aug 23 2008