A099077 - OEIS

%I #22 Feb 16 2025 08:32:54

%S 5,25,2232,4560

%N Numbers k such that pi(1).pi(2) ... pi(k-1).pi(k) is prime (dot between numbers means concatenation).

%C Number of digits of primes corresponding to the four known terms of this sequence are respectively 4,24,6127,13111. Next term is greater than 10250 and the prime corresponding to the next term has more than 32500 digits.

%C a(5) > 35000. - _Michael S. Branicky_, Nov 25 2024

%H Carlos Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_008.htm">Puzzle 8. Primes by Listing</a>, The Prime Puzzles & Problems connection.

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/IntegerSequencePrimes.html">Integer Sequence Primes</a>

%e 5 is in the sequence because pi(1).pi(2).pi(3).pi(4).pi(5)=1223 is prime.

%Y Cf. A000720, A046035, A099078, A099079, A099080.

%K nonn,base,more,changed

%O 1,1

%A _Farideh Firoozbakht_, Oct 23 2004