A243962 Primes p such that 10p + 1, 100p + 1 and 1000p + 1 are also primes.

7, 13, 19, 103, 823, 1021, 1579, 1867, 2503, 3331, 5779, 6871, 6949, 9007, 10093, 10399, 11317, 11743, 13327, 13381, 15859, 16657, 17539, 17659, 22189, 26317, 26557, 26821, 27397, 27943, 29209, 29383, 30211, 32443, 37309, 38287, 40213, 40507, 44497, 47569, 47977

Offset: 1

Author

K. D. Bajpai, Jun 16 2014

Keywords

• nonn

Examples

			7 is in the sequence because 7 is prime, 10*7 + 1 = 71 is prime, 100*7 + 1 = 701 is prime, and 1000*7 + 1 = 7001 is prime.
		

Links

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

Crossrefs

Cf. A000040, A023237, A024912.

Programs

Maple

with(numtheory):A243962:= proc() local p; p:=ithprime(n); if isprime(10*p+1) and isprime(100*p+1) and isprime(1000*p+1) then RETURN (p); fi; end: seq(A243962 (), n=1..5000);

Mathematica

Select[Prime[Range[10000]], PrimeQ[10 # + 1] && PrimeQ[100 # + 1] && PrimeQ[1000 # + 1] &]