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 A084671 #20 Dec 22 2022 07:36:53 %S A084671 5,23,67,73,157,307,389,419,449,587,661,751,1051,1229,1297,1303,1327, %T A084671 1823,1913,1999,2131,2179,2207,2239,2371,2689,2699,3067,3433,3593, %U A084671 3623,3719,3919,3943,4001,4073,4229,4241,4397,4591,4733,4919,4957,4987,5393,5449,5503 %N A084671 Primes such that the decimal concatenation of prime(n) and n is prime. %H A084671 Michael S. Branicky, <a href="/A084671/b084671.txt">Table of n, a(n) for n = 1..10000</a> %e A084671 23 is a term because 23=prime(9) and concatenation of 23 and 9 is prime. %t A084671 a=ParallelTable[Prime[k],{k,1,10^6}];k=2;Monitor[Parallelize[While[True,If[ToExpression[StringJoin[ToString/@{k,FromDigits[Position[a,k]//Flatten]}]]//PrimeQ,Print[k]];k++];k],k] (* _J.W.L. (Jan) Eerland_, Dec 22 2022 *) %o A084671 (Python) %o A084671 from itertools import islice %o A084671 from sympy import isprime, sieve %o A084671 def agen(): yield from (pn for n, pn in enumerate(sieve, 1) if isprime(int(str(pn)+str(n)))) %o A084671 print(list(islice(agen(), 52))) # _Michael S. Branicky_, Dec 22 2022 %K A084671 nonn,base %O A084671 1,1 %A A084671 _Zak Seidov_, Jun 29 2003 %E A084671 Edited by _Charles R Greathouse IV_, Apr 27 2010 %E A084671 a(45)-a(52) from _J.W.L. (Jan) Eerland_, Dec 22 2022