A077359 Primes whose external digits form a prime. Or primes from which deleting the internal digits leaves a prime.

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 223, 229, 233, 239, 263, 269, 283, 293, 307, 311, 317, 331

Offset: 1

Author

Amarnath Murthy, Nov 05 2002

Keywords

• base
• nonn

Links

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

Crossrefs

Cf. A069686, A077360.

Programs

Mathematica

edpQ[n_]:=Module[{idn=IntegerDigits[n]},PrimeQ[10idn[[1]]+idn[[-1]]]]; Join[ {2,3,5,7},Select[Prime[Range[200]],edpQ]] (* Harvey P. Dale, Nov 20 2020 *)

PARI

{exdigs(n)=local(a,j,d); d=divrem(n,10); a=d[2]; n=d[1]; j=1; while(n>10,d=divrem(n,10); n=d[1]; j=10*j); 10*n+a} forprime(p=1,335,if(isprime(exdigs(p)),print1(p,",")))

Extensions

Edited and extended by Klaus Brockhaus, Nov 06 2002