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 A383811 #9 May 27 2025 23:44:15
%S A383811 373,1913,3733,6737,7937,11353,13997,19997,23773,24113,29347,31181,
%T A383811 31193,31907,34729,37277,38237,41593,47293,59929,71971,72719,73823,
%U A383811 74177,79337,79613,82373,83773,83911,88397,100913,111773,111973,118171,118273,118747,132113,132137,139547
%N A383811 Primes which satisfy the requirements of A380943 in exactly two ways.
%C A383811 The requirements of A380943 are that primes, p_n, written in decimal representation by the concatenation of primes p and q such that the concatenation of q and p also forms a prime.
%e A383811 373 is a member since 373 is the 74th prime, p=3 and q=73, and the reverse concatenation is 733 which is the 130th prime. In another way, p=37 and q=3, and the reverse concatenation is 337, the 68th prime.
%t A383811 f[n_] := Block[{cnt = 0, id = IntegerDigits@ n, k = 1, len, p, q, qp}, len = Length@ id; While[k < len, p = Take[id, k]; q = Take[id, -len + k]; qp = FromDigits[ Join[q, p]]; If[ PrimeQ[FromDigits[p]] && PrimeQ[FromDigits[q]] && PrimeQ[qp] && IntegerLength[qp] == len, cnt++]; k++]; cnt];Select[ Prime@ Range@ 13000, f@# == 2 &]
%Y A383811 Cf. A000040, A238057, A380943, A383810, A383812, A383813, A383814, A383815, A383816.
%K A383811 nonn,base
%O A383811 1,1
%A A383811 _James C. McMahon_ and _Robert G. Wilson v_, May 17 2025