A099077 Numbers k such that pi(1).pi(2) ... pi(k-1).pi(k) is prime (dot between numbers means concatenation).

5, 25, 2232, 4560

Offset: 1

Author

Farideh Firoozbakht, Oct 23 2004

Keywords

• nonn
• base
• more

Comments

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.

a(5) > 35000. - Michael S. Branicky, Nov 25 2024

Examples

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

Links

• Carlos Rivera, Puzzle 8. Primes by Listing, The Prime Puzzles & Problems connection.
• Eric Weisstein's World of Mathematics, Integer Sequence Primes

Crossrefs

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