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A255607
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Numbers n such that both 4*n+1 and 6*n+1 are primes.
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3
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1, 3, 7, 10, 13, 18, 25, 27, 37, 45, 58, 70, 73, 87, 100, 102, 105, 112, 115, 135, 142, 153, 165, 168, 175, 177, 192, 202, 205, 213, 220, 238, 255, 258, 277, 282, 298, 300, 312, 322, 325, 352, 357, 363, 370, 373, 417, 423, 447, 465, 472, 475, 513, 520
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OFFSET
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1,2
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COMMENTS
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Numbers n such that A033570(2n) is semiprime.
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LINKS
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FORMULA
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EXAMPLE
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10 is in this sequence because 4*10+1=41 and 6*10+1=61 are primes.
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MAPLE
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MATHEMATICA
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Select[Range[600], PrimeQ[4 # + 1] && PrimeQ[6 # + 1] &]
Select[Range[600], AllTrue[{4#, 6#}+1, PrimeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Sep 22 2020 *)
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PROG
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(Magma) [n: n in [1..600] | IsPrime(6*n+1) and IsPrime(4*n+1)];
(PARI) for(n=1, 10^3, if(isprime(4*n+1)&&isprime(6*n+1), print1(n, ", "))) \\ Derek Orr, Mar 01 2015
(PARI) select( is_A255607(n)=isprime(4*n+1)&&isprime(6*n+1), [1..555]) \\ M. F. Hasler, Dec 13 2019
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CROSSREFS
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Cf. A255584: semiprimes of the form (4*n+1)*(6*n+1).
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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