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A350247 Positive integers k such that the concatenation of k and 11 is the lesser of a pair of twin primes (i.e., a term of A001359).

%I A350247 #20 Jan 20 2022 18:17:20
%S A350247 3,21,27,72,90,126,183,189,192,210,216,261,267,300,315,324,342,345,
%T A350247 360,378,387,414,477,483,540,567,633,672,681,687,714,717,744,750,777,
%U A350247 798,828,861,870,888,918,939,987,1011,1029,1038,1080,1182,1260,1266,1281
%N A350247 Positive integers k such that the concatenation of k and 11 is the lesser of a pair of twin primes (i.e., a term of A001359).
%C A350247 Every term is a multiple of 3.
%C A350247 Numbers k such that 100*k+11 and 100*k+13 are prime. - _Chai Wah Wu_, Jan 20 2022
%e A350247 311, 2111, 2711, 7211, and 9011 are terms of A001359.
%p A350247 terms := proc(n)
%p A350247    local k, p, L:
%p A350247    k, L := 0, []:
%p A350247    while numelems(L) < n do
%p A350247       k := k+1:
%p A350247       p := parse(cat(k, 11)):
%p A350247       if isprime(p) and isprime(p+2) then L := [op(L), k]: fi: od:
%p A350247    L: end:
%t A350247 Select[Range[1282], AllTrue[# + {0, 2}, PrimeQ] &[100 # + 11] &] (* _Michael De Vlieger_, Dec 21 2021 *)
%o A350247 (Python)
%o A350247 from itertools import count, islice
%o A350247 from sympy import isprime
%o A350247 def A350247_gen(startvalue=3): # generator of terms >= startvalue
%o A350247     for n in count(max(3,startvalue+(3-startvalue%3)%3),3):
%o A350247         if isprime(100*n+11) and isprime(100*n+13):
%o A350247             yield n
%o A350247 A350247_list = list(islice(A350247_gen(),20)) # _Chai Wah Wu_, Jan 20 2022
%Y A350247 Cf. A001359, A350246.
%K A350247 nonn,base
%O A350247 1,1
%A A350247 _Lorenzo Sauras Altuzarra_, Dec 21 2021