A103397 - OEIS

%I #7 Mar 30 2012 18:40:27

%S 4,9,15,21,33,38,58,65,86,106,121,129,265,511,8114,8193,16307,16853,

%T 17855,19857,31298,68037,104739,124205,131209,134149,140457,152849,

%U 252914,259918,265358,274606,417527,2498871,5291863,8424051,8743821

%N Semiprimes in A103377.

%F Intersection of A103377 with A001358.

%e 2071468241 is an element of A103377 and 2071468241= 17 * 121851073 which shows that it is a semiprime.

%t SemiprimeQ[n_]:=Plus@@FactorInteger[n][[All, 2]]?2; Clear[a]; k=9; Do[a[n]=1, {n, k+1}]; a[n_]:=a[n]=a[n-k]+a[n-k-1]; A103377=Array[a, 100] A103387=Union[Select[Array[a, 1000], PrimeQ]] A103397=Union[Select[Array[a, 300], SemiprimeQ]] N[Solve[x^10 - x - 1 == 0, x], 111][[2]]

%Y Cf. A001358, A000931, A079398, A103372-103381, A103377, A103397.

%K easy,nonn

%O 1,1

%A _Jonathan Vos Post_, Feb 15 2005