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A101793
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Primes of the form 16*k-1 such that 4*k-1 and 8*k-1 are also primes.
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8
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47, 719, 1439, 2879, 4079, 4127, 5807, 6047, 7247, 7727, 9839, 10799, 11279, 13967, 14159, 15647, 21599, 24527, 28319, 28607, 42767, 44687, 45887, 48479, 51599, 51839, 67247, 68639, 72767, 77279, 79967, 81647, 84047, 84719, 89087, 92399, 95279, 96959, 98207
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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4*3-1 = 11, 8*3-1 = 23 and 16*3-1 = 47 are primes, so 47 is a term.
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MATHEMATICA
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16#-1&/@Select[Range[10000], AllTrue[{4#-1, 8#-1, 16#-1}, PrimeQ]&] (* Harvey P. Dale, Jun 13 2015 *)
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PROG
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(PARI) is(k) = if(k % 16 == 15, my(m = k\16 + 1); isprime(4*m-1) && isprime(8*m-1) && isprime(16*m-1), 0); \\ Amiram Eldar, May 13 2024
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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Douglas Stones (dssto1(AT)student.monash.edu.au), Dec 16 2004
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STATUS
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approved
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