login
Largest prime less than 2n.
16

%I #19 Nov 16 2016 15:10:53

%S 3,5,7,7,11,13,13,17,19,19,23,23,23,29,31,31,31,37,37,41,43,43,47,47,

%T 47,53,53,53,59,61,61,61,67,67,71,73,73,73,79,79,83,83,83,89,89,89,89,

%U 97,97,101,103,103,107,109,109,113,113,113,113,113,113,113,127,127,131

%N Largest prime less than 2n.

%C a(n) = A007917(2*n) = A255313(n-1,1) = A255316(n-1,1) = A006530(A255427(n)). - _Reinhard Zumkeller_, Feb 22 2015

%H Harry J. Smith, <a href="/A060265/b060265.txt">Table of n, a(n) for n = 2..1000</a>

%p seq (prevprime(2*i+1), i=2..256);

%t Table[NextPrime[2 n, -1], {n, 2, 66}] (* _Michael De Vlieger_, Jul 04 2016 *)

%o (PARI) for (n=2, 1000, write("b060265.txt", n, " ", precprime(2*n)); ) \\ _Harry J. Smith_, Jul 03 2009

%o (Haskell)

%o a060265 = a007917 . (* 2) -- _Reinhard Zumkeller_, Feb 22 2015

%Y Apart from initial term, same as A060308.

%Y Cf. A020482, A049653, A088631, A007917, A005843, A255313.

%K nonn,easy

%O 2,1

%A _Labos Elemer_, Mar 23 2001