A033558 - OEIS

%I #16 Oct 12 2019 15:19:31

%S 0,1,1,3,3,5,3,5,7,9,9,11,9,11,13,15,15,17,15,17,19,21,17,19,21,23,25,

%T 27,27,29,25,27,29,31,33,35,33,35,37,39,39,41,39,41,43,45,41,43,45,47,

%U 49,51,47,49,51,53,55,57

%N a(n) = 2n - {smallest prime > n}.

%C By Bertrand's postulate, for n>3 a(n)>2. - _Zak Seidov_, Mar 06 2015

%H Zak Seidov, <a href="/A033558/b033558.txt">Table of n, a(n) for n = 1..1000</a>

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Bertrand%27s_postulate">Bertrand's postulate</a>

%p f := n->2*n-nextprime(n); [ seq(f(i),i=1..60) ];

%t Table[2*n-NextPrime[n],{n,60}] (* _Harvey P. Dale_, Jul 23 2018 *)

%o (PARI) vector(60, n, 2*n - nextprime(n + 1)) \\ _Zak Seidov_, Mar 06 2015

%Y Cf. A151800 (least prime > n).

%K nonn

%O 1,4

%A _N. J. A. Sloane_.