%I
%S 0,0,1,2,3,3,4,4,5,6,6,7,8,8,9,9,10,10,11,11,11,12,13,14,15,15,15,16,
%T 16,16,18,18,19,19,21,21,21,22,23,23,24,24,24,24,25,25,27,29,30,30,30,
%U 30,30,30,31,32,32,32,33,34,34,34,36,36,36,37,38,39,40
%N Number of primes less than prime(n)/2.
%C Previous name: Number of primes p such that prime(n) mod 2*p < prime(n).
%C Same as A055930, except for a(2). [Noticed by _R. J. Mathar_, Dec 15 2008, proved by _Andrey Zabolotskiy_, Oct 26 2017]
%F A079950(n, a(n) + 1) = prime(n).
%F Where defined, that is for n > 2, prime(a(n)) = A055377(prime(n)).  _Peter Munn_, Sep 18 2017
%F 0 with partial sums of A217564.  _David A. Corneth_, Oct 26 2017 (found earlier by _Peter Munn_).
%e n = 6: prime(6) = 13 and 2, 3, 5 are less than 13/2, therefore a(6) = 3.
%t Table[PrimePi[Prime[n]/2], {n, 75}] (* _Michael De Vlieger_, Sep 20 2017 *)
%o (PARI) a(n) = primepi(prime(n)/2); \\ _Michel Marcus_, Sep 20 2017
%Y Cf. A000040, A000720, A055377, A055930, A079951, A079953, A217564.
%K nonn
%O 1,4
%A _Reinhard Zumkeller_, Jan 19 2003
%E New name from _Peter Munn_, Sep 18 2017
