A141263 - OEIS

%I #26 Sep 27 2024 23:21:22

%S 2,3,5,7,11,13,17,37,79,101,107,113,131,149,151,157,167,179,181,191,

%T 199,313,337,347,353,359,373,383,389,709,727,739,757,769,787,797,919,

%U 929,1009,1021,1031,1033,1061,1069,1091,1097,1103,1109,1151,1153,1181

%N Lesser of a prime/emirp pair.

%C 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).

%C A002385 is subset of this sequence.

%H Chai Wah Wu, <a href="/A141263/b141263.txt">Table of n, a(n) for n = 1..1000</a>

%e 31 does not appear since we have already seen 13.

%t 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 *)

%o (Python)

%o from gmpy2 import next_prime, is_prime

%o A141263_list, p = [], 1

%o for _ in range(1, 10**4):

%o     p = next_prime(p)

%o     ps = int(str(p)[::-1])

%o     if p <= ps and is_prime(ps):

%o         A141263_list.append(int(p)) # _Chai Wah Wu_, Jun 11 2015

%Y Cf. A002385, A007500.

%K nonn,base

%O 1,1

%A _Artur Jasinski_, Jun 20 2008