OFFSET
1,1
COMMENTS
Resulting semiprimes in A108172.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
FORMULA
a(n) = (A108172(n) - 5)/6.
MATHEMATICA
Select[Range[3000], Plus@@Last/@FactorInteger[6# + 5] == 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+5)]; // Vincenzo Librandi, Sep 22 2012
(PARI) is(n)=bigomega(6*n+5)==2 \\ Charles R Greathouse IV, Feb 08 2017
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post and Ray Chandler, Oct 15 2005
STATUS
approved