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 A138070 #9 Dec 09 2024 09:31:49
%S A138070 3,3,3,3,1,3,3,1,1,3,3,1,4,1,3,3,1,4,4,1,3,3,1,4,1,4,1,3,3,1,4,1,1,4,
%T A138070 1,3,3,1,4,1,5,1,4,1,3,3,1,4,1,5,5,1,4,1,3,3,1,4,1,5,9,5,1,4,1,3,3,1,
%U A138070 4,1,5,9,9,5,1,4,1,3,3,1,4,1,5,9,2,9,5,1,4,1,3
%N A138070 Triangle read by rows: row n lists the successive digits of A135697(n), the palindromic number formed from the reflected decimal expansion of Pi.
%C A138070 Also, successive digits of A135697(n).
%H A138070 Paolo Xausa, <a href="/A138070/b138070.txt">Table of n, a(n) for n = 1..11325</a> (rows 1..150 of triangle, flattened).
%e A138070 Triangle begins:
%e A138070 3
%e A138070 3,3
%e A138070 3,1,3
%e A138070 3,1,1,3
%e A138070 3,1,4,1,3
%t A138070 Table[Join[#[[;; Floor[n/2]]], #[[Ceiling[n/2] ;; 1 ;; -1]]], {n, Length[#]}] & [First[RealDigits[Pi, 10, 15]]] (* _Paolo Xausa_, Dec 09 2024 *)
%Y A138070 Decimal expansion of Pi: A000796. Cf. A135697, A135698, A138071.
%K A138070 easy,nonn,tabl,base
%O A138070 1,1
%A A138070 _Omar E. Pol_, Mar 03 2008