A141263 Lesser of a prime/emirp pair.

2, 3, 5, 7, 11, 13, 17, 37, 79, 101, 107, 113, 131, 149, 151, 157, 167, 179, 181, 191, 199, 313, 337, 347, 353, 359, 373, 383, 389, 709, 727, 739, 757, 769, 787, 797, 919, 929, 1009, 1021, 1031, 1033, 1061, 1069, 1091, 1097, 1103, 1109, 1151, 1153, 1181

Offset: 1

Author

Artur Jasinski, Jun 20 2008

Keywords

• nonn
• base

Comments

From the set of numbers that are both prime and emirp choose the smaller one of each pair (whenever more than one decimal digit is involved).

A002385 is subset of this sequence.

Examples

			31 does not appear since we have already seen 13.
		

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A002385, A007500.

Programs

Mathematica

pp[n_] := Module[{nr=FromDigits[Reverse[IntegerDigits[n]]]}, If[PrimeQ[nr],Sort[{n,nr}]]]; Transpose[Rest[Union[pp/@Prime[Range[200]]]]][[1]] (* Harvey P. Dale, Dec 18 2010 *)

Python

from gmpy2 import next_prime, is_prime
A141263_list, p = [], 1
for _ in range(1, 10**4):
    p = next_prime(p)
    ps = int(str(p)[::-1])
    if p <= ps and is_prime(ps):
        A141263_list.append(int(p)) # Chai Wah Wu, Jun 11 2015