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%I #9 Nov 17 2019 15:49:23
%S 0,5,7,9,11,13,15,17,19,21,23,25,26,27,29,31,33,34,35,37,39,41,43,45,
%T 47,49,50,51,53,55,56,57,59,61,63,64,65,67,69,71,73,75,76,77,79,81,83,
%U 85,86,87,89,91,92,93,94,95,97,99,101,103,105,107,109,111,113,115,116,117,118
%N Neither n-1 nor n+1 is prime.
%C Numbers n such that n-+1 are both nonprime. Zero together with inverse hyperbolic cotangent reducible numbers.
%C Union of {0} and A099047. [From _R. J. Mathar_, Aug 09 2010]
%e a(1)=0 because 0-1=-1 and 0+1=1 are nonprime; a(2)=5 because 5-1=4 and 5+1=6 are nonprime.
%t Select[Range[0,150],!PrimeQ[#-1]&&!PrimeQ[#+1]&] (* _Harvey P. Dale_, Aug 15 2012 *)
%t Join[{0},Mean/@SequencePosition[Table[If[PrimeQ[n],0,1],{n,200}],{1,x_,1}]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Nov 17 2019 *)
%Y Cf. A084926.
%K nonn,easy
%O 1,2
%A _Juri-Stepan Gerasimov_, Mar 18 2010
%E Corrected by _Charles R Greathouse IV_, Mar 18 2010
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