A176073 Semiprimes of the form 3^k + 2^k + k + 1.

39, 2323, 6826, 179207, 14381691, 129271253, 617675543767627, 5559069156490149, 450284043329950873, 174449211045148976090134531, 5474401089420370497804607762216590113

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..14

Example

39 = 3*13 = 3^3 + 2^3 + 3 + 1.

Mathematica

f[n_] := Last/@FactorInteger[n] == {1, 1}; Select[Array[3^# + 2^# + # + 1&, 90], f[#] &]
Select[Table[3^n + 2^n + n + 1, {n, 130}], PrimeOmega[#] == 2&] (* Vincenzo Librandi, Sep 21 2012 *)

Prog

(PARI) for(n=1, 1e2, if(bigomega(t=3^n+2^n+n+1)==2, print1(t", "))) \\ Charles R Greathouse IV, Apr 16 2012
(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

Crossrefs

Sequence in context: A139191 A319490 A327589 * A145619 A027490 A323688

Adjacent sequences: A176070 A176071 A176072 * A176074 A176075 A176076

Keyword

nonn,easy

Author

Vladimir Joseph Stephan Orlovsky, Apr 07 2010

Status

approved