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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).
1
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
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
Sequence in context: A273481 A050586 A074217 * A062219 A091103 A363409
KEYWORD
nonn,base
AUTHOR
STATUS
approved