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%I #19 Sep 08 2022 08:45:52
%S 39,2323,6826,179207,14381691,129271253,617675543767627,
%T 5559069156490149,450284043329950873,174449211045148976090134531,
%U 5474401089420370497804607762216590113
%N Semiprimes of the form 3^k + 2^k + k + 1.
%H Vincenzo Librandi, <a href="/A176073/b176073.txt">Table of n, a(n) for n = 1..14</a>
%e 39 = 3*13 = 3^3 + 2^3 + 3 + 1.
%t f[n_] := Last/@FactorInteger[n] == {1,1}; Select[Array[3^# + 2^# + # + 1&, 90], f[#] &]
%t Select[Table[3^n + 2^n + n + 1, {n, 130}], PrimeOmega[#] == 2&] (* _Vincenzo Librandi_, Sep 21 2012 *)
%o (PARI) for(n=1,1e2,if(bigomega(t=3^n+2^n+n+1)==2,print1(t", "))) \\ _Charles R Greathouse IV_, Apr 16 2012
%o (Magma) IsSemiprime:=func<n | &+[d[2]: d in Factorization(n)] eq 2>; [s: n in [2..130] | IsSemiprime(s) where s is 3^n + 2^n + n + 1]; // _Vincenzo Librandi_, Sep 21 2012
%K nonn,easy
%O 1,1
%A _Vladimir Joseph Stephan Orlovsky_, Apr 07 2010
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