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 A135700 #19 Apr 30 2025 11:10:46 %S A135700 1,11,161,1661,16161,161161,1618161,16188161,161808161,1618008161, %T A135700 16180308161,161803308161,1618033308161,16180333308161, %U A135700 161803393308161,1618033993308161,16180339893308161,161803398893308161,1618033988893308161,16180339888893308161,161803398878893308161 %N A135700 Palindromes formed from the reflected decimal expansion of golden ratio phi. %C A135700 Phi = 1.61803398874989484820458683436... (see A001622). %C A135700 The number of digits of a(n) is equal to n. %e A135700 n ... Successive digits of a(n) %e A135700 1 ............ ( 1 ) %e A135700 2 ........... ( 1 1 ) %e A135700 3 .......... ( 1 6 1 ) %e A135700 4 ......... ( 1 6 6 1 ) %e A135700 5 ........ ( 1 6 1 6 1 ) %e A135700 6 ....... ( 1 6 1 1 6 1 ) %e A135700 7 ...... ( 1 6 1 8 1 6 1 ) %e A135700 8 ..... ( 1 6 1 8 8 1 6 1 ) %e A135700 9 .... ( 1 6 1 8 0 8 1 6 1 ) %e A135700 10 .. ( 1 6 1 8 0 0 8 1 6 1 ) %t A135700 gr=RealDigits[GoldenRatio, 10, 50][[1]]; (* increase for n>100 *)a[n_]:=FromDigits[Join[Take[gr, Ceiling[n/2]], Reverse[Take[gr, n-Ceiling[n/2]]]]]; Array[a, 20] (* _James C. McMahon_, Apr 29 2025 *) %Y A135700 Cf. A001622, A002113. %Y A135700 Cf. A138072, A138073. %K A135700 base,nonn %O A135700 1,2 %A A135700 _Omar E. Pol_, Mar 01 2008, Mar 28 2008