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A173083 Semiprimes q such that q^2+3 and q^2-3 are also semiprimes. 4

%I #3 Mar 31 2012 12:38:28

%S 6,226,262,302,314,334,346,382,466,482,514,538,562,734,778,842,866,

%T 886,898,926,974,1006,1046,1282,1306,1318,1322,1438,1466,1478,1574,

%U 1622,1774,1822,1838,1858,1894,1994,2302,2342,2446,2518,2578,2582,2602,2638

%N Semiprimes q such that q^2+3 and q^2-3 are also semiprimes.

%F {A001358(j): A074985(j)-3 in A001358 and A074985(j)+3 in A001358}. [R. J. Mathar, Mar 11 2010]

%e 6^2-3=33 = 3*11 and 6^2+3=39 = 3*13 are semiprimes derived from q=6, so q=6 is in the sequence.

%t f[n_]:=Last/@FactorInteger[n]=={1,1}||Last/@FactorInteger[n]=={2}; lst={}; Do[If[f[n], a=n^2-3;b=n^2+3;If[f[a]&&f[b],AppendTo[lst,n]]],{n,8!}]; lst

%Y Cf. A001358, A173082

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, Feb 09 2010

%E Definition rephrased - _R. J. Mathar_, Mar 11 2010

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