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 A103741 a(n) is a non-palindromic composite located between twin primes whose reverse, which is less than it, is also located between twin primes. 3
 60, 240, 270, 600, 810, 822, 2130, 2340, 2802, 8010, 8220, 8430, 8838, 8862, 20550, 22740, 23202, 23370, 23910, 25410, 26880, 27240, 28410, 28572, 28662, 29022, 29760, 80472, 81702, 81930, 81972, 82140, 82530, 83220, 83340, 83640, 85620 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE 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. MATHEMATICA 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 *) npcQ[n_]:=Module[{ridn=FromDigits[Reverse[IntegerDigits[n]]]}, ridn

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Last modified October 23 08:57 EDT 2019. Contains 328345 sequences. (Running on oeis4.)