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A032731
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Numbers k such that k prefixed by '6' and followed by '9' is a prime.
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0
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1, 5, 19, 22, 26, 29, 32, 35, 37, 38, 44, 46, 52, 56, 59, 61, 65, 67, 68, 70, 71, 77, 82, 86, 89, 94, 95, 109, 112, 116, 133, 137, 140, 146, 151, 155, 160, 172, 181, 187, 190, 194, 197, 203, 209, 211, 212, 218, 221, 229, 245, 253, 254, 263, 265, 281, 286, 292
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OFFSET
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1,2
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LINKS
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MATHEMATICA
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Select[Range@300, PrimeQ@FromDigits@Flatten[{6, IntegerDigits@#, 9}]&] (* Giorgos Kalogeropoulos, Jul 28 2021 *)
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PROG
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(Python)
from sympy import isprime
def ok(n): return isprime(int('6'+str(n)+'9'))
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CROSSREFS
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Subsequence of A001651 (not divisible by 3).
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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