A240696 Prime numbers n such that replacing each digit d in the decimal expansion of n with its 9's complement produces a prime.

2, 7, 97, 997, 99999999999999997

Offset: 1

Author

Michel Lagneau, Apr 10 2014

Keywords

• nonn
• base

Comments

a(n) = {2} union {primes of the form 10^n - 3} = {2} union {A093172}.

Primes p such that A061601(p) is also prime.

The next term has 140 digits.

Examples

			997 is in the sequence because 997 becomes (002) = 2, which is prime.
		

Crossrefs

Cf. A093172, A173833.

Programs

Mathematica

lst={};f[n_]:=Block[{a=IntegerDigits[Prime[n]],b="",k=1,l},l=Length[a];While[k