A084667 - OEIS

%I #46 Sep 08 2022 08:45:11

%S 23,47,613,1237,1759,1861,2383,27103,30113,35149,36151,41179,42181,

%T 45197,46199,54251,56263,57269,58271,61283,71353,82421,83431,85439,

%U 92479,93487,99523,115631,117643,119653,121661,123677,127709,136769,141811,145829,147853

%N Primes which are a concatenation of n and prime(n).

%C Is the sequence infinite? - _Zak Seidov_, Nov 19 2013

%H Zak Seidov, <a href="/A084667/b084667.txt">Table of n, a(n) for n = 1..20000</a>

%e a(3) = 613 because prime(6) = 13 and 613 is prime,

%e a(1000) = 761077477 because prime(7610) = 77477 and 761077477 is prime.

%e a(20000) = 2092142886529 because prime(209214) = 2886529 and 2092142886529 is prime.

%t Select[Table[FromDigits[Flatten[{IntegerDigits[n], IntegerDigits[Prime[n]]}]], {n, 1, 500}], PrimeQ] (* _Alonso del Arte_, Sep 22 2004 *)

%o (Magma) [p: n in [1..200] | IsPrime(p) where p is Seqint(Intseq(NthPrime(n)) cat Intseq(n))]; // _Bruno Berselli_, Sep 15 2015

%o (PARI) lista(NN) = for(k=1,NN,p=prime(k);if(isprime(j=k*10^#digits(p)+p),print1(j, ", "))) \\ _Jinyuan Wang_, Apr 05 2019

%Y Cf. A084669.

%K nonn,base

%O 1,1

%A _Zak Seidov_, Jun 29 2003