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A020472
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Primes that contain digits 8 and 9 only.
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35
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89, 8999, 89899, 89989, 98899, 98999, 99989, 888989, 898889, 989999, 998989, 8888989, 8889889, 8988989, 8989999, 8998889, 8999899, 9888889, 9889889, 9899999, 9989899, 9999889, 88888999, 88898989, 88989899, 89888989, 89889889, 89898889, 89999999, 98888989
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OFFSET
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1,1
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COMMENTS
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Or, primes with minimal digit 8.
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LINKS
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MATHEMATICA
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Select[Prime[Range[80000]], Min[IntegerDigits[#]] == 8 &] (* Zak Seidov, May 07 2005 *)
Flatten[Table[Select[FromDigits/@Tuples[{8, 9}, n], PrimeQ], {n, 8}]] (* Vincenzo Librandi, Jul 27 2012 *)
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PROG
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(PARI) for(nd=1, 9, p=vector(nd, i, 10^(nd-i))~; forvec(v=vector(nd, i, [8+(i==nd), 9]), isprime(v*p) && print1(v*p", "))) \\ M. F. Hasler, Mar 18 2010
(Python)
from sympy import isprime
from itertools import count, islice, product
def agen(): # generator of terms
for d in count(2):
for first in product("89", repeat=d-1):
t = int("".join(first) + "9")
if isprime(t): yield t
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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