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A210514 Prime numbers generated by concatenating k, k, and 9. 2
229, 449, 11119, 14149, 22229, 28289, 31319, 37379, 44449, 49499, 52529, 56569, 67679, 70709, 71719, 80809, 86869, 89899, 94949, 95959, 1061069, 1101109, 1131139, 1151159, 1161169, 1191199, 1241249, 1251259, 1331339, 1401409, 1431439, 1481489, 1571579, 1601609 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
This series is similar to A030458 and A052089.
Base considered is 10.
LINKS
EXAMPLE
For k=2, a(1)= 229.
For k=4, a(2)= 449.
For k=11, a(3)= 11119.
For k=14, a(4)= 14149.
MATHEMATICA
Select[Table[FromDigits[Flatten[Join[IntegerDigits/@{n, n}, {9}]]], {n, 200}], PrimeQ] (* Harvey P. Dale, Apr 23 2015 *)
PROG
(Python)
import numpy as np
from functools import reduce
def factors(n):
return reduce(list.__add__, ([i, n//i] for i in range(1, int(n**0.5) + 1) if n % i == 0))
for i in range(1, 2000):
p1=int(str(i)+str(i)+"1")
if len(factors(p1))<3:
print(p1, end=', ')
(Python)
from sympy import isprime
from itertools import count, islice
def agen(): yield from filter(isprime, (int(str(k)+str(k)+'9') for k in count(1)))
print(list(islice(agen(), 34))) # Michael S. Branicky, Jul 26 2022
CROSSREFS
Sequence in context: A139512 A142263 A142608 * A142665 A124684 A332740
KEYWORD
base,nonn,easy
AUTHOR
Abhiram R Devesh, Jan 26 2013
EXTENSIONS
a(27) and beyond from Michael S. Branicky, Jul 26 2022
STATUS
approved

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Last modified February 25 11:09 EST 2024. Contains 370324 sequences. (Running on oeis4.)