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A176073 Semiprimes of the form 3^n + 2^n + n + 1. 1
39, 2323, 6826, 179207, 14381691, 129271253, 617675543767627, 5559069156490149, 450284043329950873, 174449211045148976090134531, 5474401089420370497804607762216590113 (list; graph; refs; listen; history; text; internal format)
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 2912

CROSSREFS

Sequence in context: A158768 A139191 A319490 * A145619 A027490 A266453

Adjacent sequences:  A176070 A176071 A176072 * A176074 A176075 A176076

KEYWORD

nonn,easy

AUTHOR

Vladimir Joseph Stephan Orlovsky, Apr 07 2010

STATUS

approved

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Last modified October 15 16:14 EDT 2018. Contains 316236 sequences. (Running on oeis4.)