A104045 Numbers k such that k9 is prime and k is a multiple of ten.

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

Author

Parthasarathy Nambi, Mar 01 2005

Keywords

• base
• nonn

Examples

			If k =  10, then k9 =  109 (prime).
If k = 160, then k9 = 1609 (prime).
If k = 320, then k9 = 3209 (prime).
		

Links

• Michael S. Branicky, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A030433, A008592, A102700, A166560 (resulting primes).

Programs

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 *)

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