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 A172414 #12 Aug 18 2022 10:30:41
%S A172414 1,1,1,1,2,2,2,2,2,5,5,5,5,5,5,5,14,14,14,14,14,14,14,14,14,42,42,42,
%T A172414 42,42,42,42,42,42,42,42,132,132,132,132,132,132,132,132,132,132,132,
%U A172414 132,132,429,429,429,429,429,429,429,429,429,429,429,429,429,429,429
%N A172414 Triangle read by rows: Catalan number C(n) repeated 2*n+1 times.
%F A172414 T(n,k) = A000108(n). - _R. J. Mathar_, Nov 03 2016
%F A172414 Sum_{n>=0} 1/a(n) = 6 + 44*Pi/(27*sqrt(3)). - _Amiram Eldar_, Aug 18 2022
%e A172414 Triangle begins:
%e A172414 ......1
%e A172414 ....1,1,1
%e A172414 ..2,2,2,2,2
%e A172414 5,5,5,5,5,5,5,
%t A172414 Table[PadRight[{}, 2*n + 1, CatalanNumber[n]], {n, 0, 8}] // Flatten (* _Amiram Eldar_, Aug 18 2022, after _Harvey P. Dale_ at A172417 *)
%Y A172414 Cf. A000108, A001700 (row sums), A172417, A168256.
%K A172414 nonn,tabf,easy,less
%O A172414 0,5
%A A172414 _Mark Dols_, Feb 02 2010
%E A172414 Offset corrected by _R. J. Mathar_, Nov 03 2016
%E A172414 Data corrected and extended by _Amiram Eldar_, Aug 18 2022