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 A383814 #7 Jun 06 2025 18:40:10
%S A383814 2,37,373,19937,257931013,4199993923
%N A383814 Least number which satisfies the requirements of A380943 in exactly n ways.
%C A383814 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 A383814 See the examples in A383810 through A383813.
%t A383814 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];a[n_]:=Module[{k=1},While[f[Prime[k]]!=n,k++];Prime[k]];Array[a,4,0]
%Y A383814 Cf. A000040, A173935, A380943, A383810, A383811, A383812, A383813, A383815, A383816.
%K A383814 nonn,base,more
%O A383814 0,1
%A A383814 _James C. McMahon_ and _Robert G. Wilson v_, May 29 2025