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Sums of two consecutive semiprimes.
4

%I #9 Jun 22 2020 19:44:39

%S 19,29,43,51,67,69,77,115,171,173,187,189,237,243,245,267,283,285,291,

%T 317,355,403,405,411,427,429,435,437,507,597,603,605,653,669,723,763,

%U 787,789,891,893,907,963,1003,1029,1053,1075,1085,1107,1131,1245,1267

%N Sums of two consecutive semiprimes.

%C First 16 terms:19,29,43,51,67,69,77,115,171,173,187,189,237,243,245,267 are the same as in A157483.

%C These are sums of two consecutive integers which are both semiprimes, whereas A118717 are sums of two semiprimes which are adjacent (consecutive) in A001358. [From _R. J. Mathar_, Mar 18 2010]

%H Harvey P. Dale, <a href="/A173966/b173966.txt">Table of n, a(n) for n = 1..1000</a>

%t f[n_]:=Last/@FactorInteger[n]=={1,1}||Last/@FactorInteger[n]=={2};lst={};Do[If[f[n],If[f[n+1],AppendTo[lst,2*n+1]]],{n,7!}];lst

%t Total/@Select[Partition[Select[Range[700],PrimeOmega[#]==2&],2,1],#[[2]]- #[[1]] == 1&] (* _Harvey P. Dale_, Jun 22 2020 *)

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, Mar 03 2010