OFFSET
1,2
COMMENTS
This is A006254 (numbers n such that 2n-1 is prime) with a leading 1. - Lambert Klasen (lambert.klasen(AT)gmx.net), Nov 06 2005
Same as smallest k such that prime(n) divides C(2k,k). - Jonathan Sondow, Jan 20 2016
Positions of records in A046112. - Hugo Pfoertner, Jul 11 2019
LINKS
Ray Chandler, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = ceiling((prime_n)/2). - Robert G. Wilson v, Nov 07 2005
MAPLE
seq(ceil(ithprime(i)/2), i=1..100); # Robert Israel, Jan 20 2016
MATHEMATICA
Table[ Ceiling[ Prime[n]/2], {n, 65}] (* Robert G. Wilson v *)
PROG
(PARI) a(n)=(prime(n)+1)\2 \\ Charles R Greathouse IV, Sep 16 2015
(Python)
from sympy import prime
def A111333(n): return prime(n)+1>>1 # Chai Wah Wu, Aug 02 2024
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Giovanni Teofilatto, Nov 05 2005
EXTENSIONS
More terms from Robert G. Wilson v, Nov 07 2005
STATUS
approved