This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A111333 #25 Jul 08 2025 11:28:29
%S A111333 1,2,3,4,6,7,9,10,12,15,16,19,21,22,24,27,30,31,34,36,37,40,42,45,49,
%T A111333 51,52,54,55,57,64,66,69,70,75,76,79,82,84,87,90,91,96,97,99,100,106,
%U A111333 112,114,115,117,120,121,126,129,132,135,136,139,141,142,147,154,156,157
%N A111333 Number of odd numbers <= n-th prime.
%C A111333 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
%C A111333 Same as smallest k such that prime(n) divides C(2k,k). - _Jonathan Sondow_, Jan 20 2016
%C A111333 Positions of records in A046112. - _Hugo Pfoertner_, Jul 11 2019
%H A111333 Ray Chandler, <a href="/A111333/b111333.txt">Table of n, a(n) for n = 1..10000</a>
%F A111333 a(n) = ceiling((prime_n)/2). - _Robert G. Wilson v_, Nov 07 2005
%p A111333 seq(ceil(ithprime(i)/2), i=1..100); # _Robert Israel_, Jan 20 2016
%t A111333 Table[ Ceiling[ Prime[n]/2], {n, 65}] (* _Robert G. Wilson v_, Nov 07 2005 *)
%o A111333 (PARI) a(n)=(prime(n)+1)\2 \\ _Charles R Greathouse IV_, Sep 16 2015
%o A111333 (Python)
%o A111333 from sympy import prime
%o A111333 def A111333(n): return prime(n)+1>>1 # _Chai Wah Wu_, Aug 02 2024
%Y A111333 Cf. A006254, A046112, A049990, A062875.
%K A111333 nonn,easy
%O A111333 1,2
%A A111333 _Giovanni Teofilatto_, Nov 05 2005
%E A111333 More terms from _Robert G. Wilson v_, Nov 07 2005