A227916 Primes that remain prime when the leftmost digit is removed.

13, 17, 23, 37, 43, 47, 53, 67, 73, 83, 97, 103, 107, 113, 131, 137, 167, 173, 179, 197, 211, 223, 229, 241, 271, 283, 307, 311, 313, 317, 331, 337, 347, 353, 359, 367, 373, 379, 383, 389, 397, 419, 431, 443, 461, 467, 479, 503, 523, 541, 547, 571, 607, 613, 617

Offset: 1

Author

K. D. Bajpai, Oct 13 2013

Keywords

• nonn
• base

Examples

			a(11)= 97 which is prime. Removing the leftmost digit gives 7, also prime.
a(28)= 311 which is prime. Removing the leftmost digit gives 11, also prime.
		

Links

• K. D. Bajpai, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000040 (prime numbers), A024785 (left-truncatable primes).

Cf. A137812 (left- or right-truncatable primes).

Cf. A227919 (primes which remain prime when rightmost digit is removed).

Programs

Maple

KD:= proc() local a,b,c,d; a:=ithprime(n);b:=length(a); c:=floor(a/(10^(b-1)));d:=a-c*(10^(b-1));if isprime(d) then return(a):fi; end:seq(KD(),n=1..5000);