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A112775
Numbers n such that 6n+1 is semiprime.
4
4, 8, 9, 14, 15, 19, 20, 22, 24, 28, 31, 34, 36, 39, 41, 42, 43, 44, 48, 49, 50, 53, 59, 60, 65, 67, 69, 71, 74, 75, 78, 80, 82, 84, 85, 86, 88, 89, 92, 93, 94, 97, 98, 108, 109, 111, 113, 114, 116, 117, 120, 124, 127, 130, 132, 133, 136, 139, 140, 144, 145, 148, 149
OFFSET
1,1
COMMENTS
Resulting semiprimes in A112771.
LINKS
FORMULA
a(n) = (A112771(n) - 1)/6.
MATHEMATICA
Select[Range[200], Plus@@Last/@FactorInteger[6#+1]==2&] (* Vincenzo Librandi, Sep 22 2012 *)
PROG
(Magma) IsSemiprime:=func<n | &+[k[2]: k in Factorization(n)] eq 2>; [n: n in [2..150] | IsSemiprime(6*n+1)]; // Vincenzo Librandi, Sep 22 2012
CROSSREFS
Sequence in context: A060299 A120512 A046954 * A107747 A121763 A110087
KEYWORD
easy,nonn
AUTHOR
STATUS
approved