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%I #8 Mar 28 2015 22:24:48
%S 60,240,270,600,810,822,2130,2340,2802,8010,8220,8430,8838,8862,20550,
%T 22740,23202,23370,23910,25410,26880,27240,28410,28572,28662,29022,
%U 29760,80472,81702,81930,81972,82140,82530,83220,83340,83640,85620
%N a(n) is a non-palindromic composite located between twin primes whose reverse, which is less than it, is also located between twin primes.
%e 810 is in the sequence as it is between the twin primes 809 and 811 and its reverse, 018 or 18, is also between the twin primes 17 and 19.
%t fQ[n_] := Block[{np = FromDigits[ Reverse[ IntegerDigits[n]]]}, If[np < n && PrimeQ[n - 1] && PrimeQ[n + 1] && PrimeQ[np - 1] && PrimeQ[np + 1], True, False]]; Select[ Range[2, 87220, 2], fQ[ # ] &] (* _Robert G. Wilson v_, Mar 30 2005 *)
%t npcQ[n_]:=Module[{ridn=FromDigits[Reverse[IntegerDigits[n]]]},ridn<n && And@@PrimeQ[ {ridn-1,ridn+1}]]; Select[Mean/@Select[Partition[ Prime[ Range[ 2,8500]], 2,1], Last[#]-First[#]==2&],npcQ] (* _Harvey P. Dale_, Oct 19 2012 *)
%K base,nonn
%O 1,1
%A _Ray G. Opao_, Mar 28 2005
%E Corrected and extended by _Robert G. Wilson v_, Mar 30 2005
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