|
%I #3 Mar 31 2012 12:38:28
%S 6,51,65,115,133,141,159,187,201,209,213,287,291,295,327,339,361,407,
%T 411,413,471,493,511,519,537,559,579,597,633,649,687,695,723,799,813,
%U 831,835,871,917,939,1007,1041,1047,1079,1135,1167,1189,1195,1199,1227
%N Semiprimes q such that q^2+2 and q^2-2 are also semiprimes.
%F {A001358(j): A074985(j)-2 in A001358 and A074985(j)+2 in A001358}. [R. J. Mathar, Mar 11 2010]
%e 6^2-2=34 = 2*17 and 6^2+2=38 = 2*19 are semiprimes derived from the semiprime 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^2-2;b=n^2+2;If[f[a]&&f[b],AppendTo[lst,n]]],{n,8!}]; lst
%Y Cf. A001358
%K nonn
%O 1,1
%A _Vladimir Joseph Stephan Orlovsky_, Feb 09 2010
%E Definition rephrased - _R. J. Mathar_, Mar 11 2010
|
