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 A135698 #14 Dec 09 2024 09:36:21
%S A135698 3,313,31413,3141413,314151413,31415951413,3141592951413,
%T A135698 314159262951413,31415926562951413,3141592653562951413,
%U A135698 314159265353562951413,31415926535853562951413,3141592653589853562951413,314159265358979853562951413,31415926535897979853562951413
%N A135698 Palindromes with odd number of digits formed from the reflected decimal expansion of Pi.
%C A135698 Pi = 3.14159265358979323846264338327... (see A000796).
%C A135698 The number of digits of a(n) is equal to 2n - 1.
%C A135698 The first five members of this sequence are in the example of A119351.
%H A135698 G. C. Greubel, <a href="/A135698/b135698.txt">Table of n, a(n) for n = 1..250</a>
%e A135698 n ........... a(n)
%e A135698 1 ............ 3
%e A135698 2 ........... 313
%e A135698 3 .......... 31413
%e A135698 4 ......... 3141413
%e A135698 5 ........ 314151413
%e A135698 6 ....... 31415951413
%e A135698 7 ...... 3141592951413
%e A135698 8 ..... 314159262951413
%e A135698 9 .... 31415926562951413
%e A135698 10 .. 3141592653562951413
%t A135698 pinxt[n_]:=With[{pid=RealDigits[Pi,10,20][[1]]},Module[{a=Take[pid,n]}, FromDigits[Join[a,Reverse[Most[a]]]]]]; Table[pinxt[n],{n,1,15}] (* _Harvey P. Dale_, Oct 06 2011 *)
%Y A135698 Cf. A000796, A002113, A119351.
%Y A135698 Cf. A135697, A039954.
%K A135698 base,nonn
%O A135698 1,1
%A A135698 _Omar E. Pol_, Mar 01 2008, Mar 28 2008
%E A135698 More terms from _Harvey P. Dale_, Oct 06 2011