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A104045
Numbers k such that k9 is prime and k is a multiple of ten.
2
10, 40, 50, 70, 80, 100, 110, 140, 160, 170, 230, 260, 290, 310, 320, 370, 440, 490, 500, 520, 530, 670, 710, 730, 800, 820, 860, 910, 920, 1000, 1070, 1090, 1190, 1210, 1240, 1280, 1300, 1310, 1330, 1370, 1400, 1580, 1720, 1750, 1760, 1790, 1900, 1930, 1960, 1970, 2050, 2080, 2210
OFFSET
1,1
LINKS
EXAMPLE
If k = 10, then k9 = 109 (prime).
If k = 160, then k9 = 1609 (prime).
If k = 320, then k9 = 3209 (prime).
MAPLE
select(n-> isprime(10*n+9), [10*i$i=1..300])[]; # Alois P. Heinz, Jan 19 2024
MATHEMATICA
Select[Range[10, 2210, 10], PrimeQ[FromDigits[Prepend[{9}, #]]]&] (* James C. McMahon, Jan 19 2024 *)
PROG
(Python)
from sympy import isprime
from itertools import count, islice
def agen(): yield from (k for k in count(10, 10) if isprime(10*k+9))
print(list(islice(agen(), 53))) # Michael S. Branicky, Jan 19 2024
CROSSREFS
Cf. A030433, A008592, A102700, A166560 (resulting primes).
Sequence in context: A197705 A306413 A187205 * A102546 A352777 A108777
KEYWORD
base,nonn
AUTHOR
Parthasarathy Nambi, Mar 01 2005
STATUS
approved