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

1,1

Links

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

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

Adjacent sequences: A104042 A104043 A104044 * A104046 A104047 A104048

Keyword

base,nonn

Author

Parthasarathy Nambi, Mar 01 2005

Status

approved