A166501 Primes p such that (p reversed)+4 is also a prime.

3, 7, 31, 73, 79, 97, 313, 331, 349, 379, 397, 541, 571, 709, 739, 757, 769, 937, 967, 3037, 3061, 3067, 3121, 3163, 3187, 3217, 3229, 3253, 3313, 3319, 3361, 3433, 3457, 3529, 3547, 3613, 3631, 3643, 3673, 3739, 3769, 3847, 3889, 5011, 5023, 5101, 5107

Offset: 1

Author

Vincenzo Librandi, Oct 15 2009

Keywords

• nonn
• base
• less

Examples

			73 is in the sequence because 37+4=41 prime.
331 is in the sequence because 133+4=137 prime.
3457 is in the sequence because 7543+4=7547 prime.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Programs

Magma

[p: p in PrimesUpTo(6000) | IsPrime(q+4) where q is Seqint(Reverse(Intseq(p)))]; // Vincenzo Librandi, Sep 15 2013

Mathematica

Select[Prime[Range[700]],PrimeQ[FromDigits[Reverse[IntegerDigits[#]]]+ 4]&] (* Harvey P. Dale, May 21 2012 *)
Select[Prime[Range[700]],PrimeQ[IntegerReverse[#]+4]&] (* Harvey P. Dale, Mar 16 2023 *)

Formula

{p = A000040(i): A004087(i)+4 in A000040}. - R. J. Mathar, Oct 16 2009

Extensions

Keyword:base added, 3163 inserted, sequence extended by R. J. Mathar, Oct 16 2009