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

1,1

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

Links

Table of n, a(n) for n=1..51.

Example

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

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 *)

Prog

(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

Crossrefs

Cf. A001359, A350246.

Sequence in context: A273481 A050586 A074217 * A062219 A091103 A363409

Adjacent sequences: A350244 A350245 A350246 * A350248 A350249 A350250

Keyword

nonn,base

Author

Lorenzo Sauras Altuzarra, Dec 21 2021

Status

approved