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a(n) = prime(2*n) - 2*prime(n).
17

%I #15 Oct 01 2021 18:49:51

%S -1,1,3,5,7,11,9,15,15,13,17,15,19,21,19,25,21,29,29,31,35,35,33,45,

%T 35,37,45,49,53,55,39,49,43,59,51,57,59,57,63,63,63,71,61,71,69,81,69,

%U 57,67,83,91,91,95,91,87,87,81,99,93,97,107,97,87,97,107,109,95,95,93,111,115,109,105,111,105,115,109,117,127,123,115

%N a(n) = prime(2*n) - 2*prime(n).

%C a(n) = A022457(n) for n > 1.

%C a(n) = A031215(n)-A100484(n) = A072473(n)-A000040(n); see A179740 for primes. - _Reinhard Zumkeller_, Jul 25 2010

%C Asymptotically, a(n) ~ log(4) n, with log(4) = 2 log 2 = 1.38629436111989... = A016627. - _M. F. Hasler_, Oct 19 2013

%H Harry J. Smith, <a href="/A066066/b066066.txt">Table of n, a(n) for n = 1..1000</a>

%t Table[Prime[2n]-2Prime[n],{n,100}] (* _Harvey P. Dale_, Aug 21 2016 *)

%o (PARI) { for (n = 1, 1000, a=prime(2*n) - prime(n)*2; write("b066066.txt", n, " ", a) ) } \\ _Harry J. Smith_, Nov 09 2009

%o (PARI) A066066(n)=prime(2*n)-2*prime(n) \\ _M. F. Hasler_, Oct 19 2013

%K sign

%O 1,3

%A _Reinhard Zumkeller_, Dec 01 2001