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

1,1

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.

Links

Table of n, a(n) for n=1..5.

Example

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

Mathematica

lst={}; f[n_]:=Block[{a=IntegerDigits[Prime[n]], b="", k=1, l}, l=Length[a]; While[k<l+1, b=StringJoin[b, ToString[9-a[[k]]]]; k++]; ToExpression[b]]; Do[If[PrimeQ[f[n]], AppendTo[lst, Prime[n]]], {n, 1, 10^6}]; lst

Crossrefs

Cf. A093172, A173833.

Sequence in context: A112290 A072059 A308961 * A102344 A087589 A002812

Adjacent sequences: A240693 A240694 A240695 * A240697 A240698 A240699

Keyword

nonn,base

Author

Michel Lagneau, Apr 10 2014

Status

approved