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 A261493 #17 Jan 15 2018 15:32:26 %S A261493 2,232,23532,2357532,2357117532,235711101117532,235711101131101117532, %T A261493 235711101131151131101117532,235711101131151181151131101117532, %U A261493 235711101131151181191181151131101117532,235711101131151181191313191181151131101117532 %N A261493 Palindromes that are concatenation of palindromic prime numbers in increasing order up to the n-th and then in decreasing order. %C A261493 Subsequence of A043037. %e A261493 For n=6, the first 6 palindromic primes are 2,3,5,7,11,101. Relevant subsequence that produce a(6) is 2,3,5,7,11,101,11,7,5,3,2. Concatenation of items with that order determines a(6) = 235711101117532. %t A261493 palQ[n_] := Reverse[idn = IntegerDigits@ n] == idn; s = Select[ Prime@ Range@ 1000, palQ]; f[n_] := FromDigits@ Flatten[ IntegerDigits@# & /@ Join[ Take[s, n], Reverse@ Take[s, n - 1]]]; Array[f, 11] (* _Robert G. Wilson v_, Aug 24 2015 *) %Y A261493 Cf. A002385, A048677. %K A261493 nonn,easy,base %O A261493 1,1 %A A261493 _Altug Alkan_, Aug 21 2015