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 A084429 #20 Aug 24 2024 05:49:19
%S A084429 14,15,23,25,37,39,44,54,55,70,79,88,90,98,102,118,123,134,136,143,
%T A084429 144,151,174,182,202,209,215,226,230,232,245,254,256,257,258,262,264,
%U A084429 267,272,284,287,297,300
%N A084429 Integers m such that the base-10 digit concatenation 4//m//3//m//2//m//1 is prime.
%C A084429 I called this sequence f4i and defined similar sequences {fni} in the comments in A083660: fni(m) is the m-th nonnegative integer k such that the concatenation fi(n, k) = n//k//n-1//k// ...//3//k//2//k//1 is prime. By this definition f2i = A032702.
%e A084429 a(3)=23 because 23 is the third nonnegative integer m such that fi(4,m) = fi(4,23) = 4 // 23 // 3 // 23 // 2 // 23 // 1 = 4233232231 is prime.
%t A084429 Do[If[PrimeQ[FromDigits[Join[{4}, IntegerDigits[n], {3}, IntegerDigits[n], {2}, IntegerDigits[n], {1}]]], v=Insert[v, n, -1]], {n, 300}]; v
%Y A084429 Cf. A083660, A032702.
%K A084429 easy,base,nonn
%O A084429 1,1
%A A084429 _Farideh Firoozbakht_, Jun 27 2003