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n-th even semiprime minus n-th semiprime.
1

%I #8 Sep 07 2012 17:40:36

%S 0,0,1,4,8,11,13,16,21,32,29,40,47,48,55,60,69,71,79,85,88,96,101,109,

%T 120,125,124,129,132,139,163,169,180,183,192,191,199,208,215,225,236,

%U 239,253,253,260,257,280,303,309,312,311,320,323,341,348,357,361,364

%N n-th even semiprime minus n-th semiprime.

%H Harvey P. Dale, <a href="/A175511/b175511.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n)=A100484(n)-A001358(n).

%t Module[{sps=Select[Range[600],PrimeOmega[#]==2&],evs},evs= Select[ sps, EvenQ]; #[[1]]-#[[2]]&/@Thread[{evs,Take[sps,Length[evs]]}]] (* _Harvey P. Dale_, Sep 07 2012 *)

%Y Cf. A131634.

%K nonn

%O 1,4

%A _Juri-Stepan Gerasimov_, Jun 03 2010

%E Entries checked by _R. J. Mathar_, Aug 12 2010