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%I #16 May 12 2022 15:22:41
%S 0,1,1,1,2,2,2,2,2,2,3,3,3,3,3,3,4,4,4,4,4,4,5,5,5,5,5,5,6,6,6,6,6,6,
%T 6,6,6,6,6,6,7,7,7,7,7,7,8,8,8,8,8,8,9,9,9,9,9,9,10,10,10,10,10,10,10,
%U 10,10,10,10,10,11,11,11,11,11,11,11,11,11,11,11,11,12,12,12,12,12,12,13,13
%N Number of primes p <= n that are congruent to 2 modulo 3.
%H Jianing Song, <a href="/A340764/b340764.txt">Table of n, a(n) for n = 1..10000</a>
%F A340763(n) + a(n) = A000720(n) - 1 for n >= 3.
%e There are 13 primes <= 100 that are congruent to 2 modulo 3, namely 2, 5, 11, 17, 23, 29, 41, 47, 53, 59, 71, 83, 89, so a(100) = 13.
%t Accumulate[Table[If[PrimeQ[n]&&Mod[n,3]==2,1,0],{n,90}]] (* _Harvey P. Dale_, May 12 2022 *)
%o (PARI) a(n) = sum(i=1, n, isprime(i) && (i%3==2))
%Y Cf. A003627, A340763, A340767, A066339, A066490.
%K nonn,easy
%O 1,5
%A _Jianing Song_, Apr 28 2021
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