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).

3, 21, 27, 72, 90, 126, 183, 189, 192, 210, 216, 261, 267, 300, 315, 324, 342, 345, 360, 378, 387, 414, 477, 483, 540, 567, 633, 672, 681, 687, 714, 717, 744, 750, 777, 798, 828, 861, 870, 888, 918, 939, 987, 1011, 1029, 1038, 1080, 1182, 1260, 1266, 1281

Offset: 1

Author

Lorenzo Sauras Altuzarra, Dec 21 2021

Keywords

• nonn
• base

Comments

Every term is a multiple of 3.

Numbers k such that 100*k+11 and 100*k+13 are prime. - Chai Wah Wu, Jan 20 2022

Examples

			311, 2111, 2711, 7211, and 9011 are terms of A001359.
		

Crossrefs

Cf. A001359, A350246.

Programs

Maple

terms := proc(n)
   local k, p, L:
   k, L := 0, []:
   while numelems(L) < n do
      k := k+1:
      p := parse(cat(k, 11)):
      if isprime(p) and isprime(p+2) then L := [op(L), k]: fi: od:
   L: end:

Mathematica

Select[Range[1282], AllTrue[# + {0, 2}, PrimeQ] &[100 # + 11] &] (* Michael De Vlieger, Dec 21 2021 *)

Python

from itertools import count, islice
from sympy import isprime
def A350247_gen(startvalue=3): # generator of terms >= startvalue
    for n in count(max(3,startvalue+(3-startvalue%3)%3),3):
        if isprime(100*n+11) and isprime(100*n+13):
            yield n
A350247_list = list(islice(A350247_gen(),20)) # Chai Wah Wu, Jan 20 2022