login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A249775 Least prime p such that the concatenation of primes from prime(n) to p is prime. 1

%I

%S 3,0,11,19,17,79,23,151,67,53,37,107,47,131,67,71,83,0,79,137,293,131,

%T 89,101,109,113,283,149,12923,149,317,181,1193,157,163,157,163,193,

%U 173,18041,307,269,227,0,2897,211,257,331,359,239,239,251,599,257,263,269,1531,277,313,379,1259

%N Least prime p such that the concatenation of primes from prime(n) to p is prime.

%C a(n) > 40000 or 0 for n = 2, 18, and 44.

%e For n = 3, prime(3) = 5. 57 is not prime. 5711 is prime. Since 5711 = 5//7//11, a(3) = 11.

%o (PARI) a(n)=s=Str(prime(n));forprime(p=prime(n)+1,40000,s=concat(s,p); if(ispseudoprime(eval(s)),return(p)));0

%o for(n=1,50,print1(a(n),", "))

%Y Cf. A249774.

%K nonn,base

%O 1,1

%A _Derek Orr_, Nov 05 2014

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 6 22:42 EST 2021. Contains 349567 sequences. (Running on oeis4.)