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A340764
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Number of primes p <= n that are congruent to 2 modulo 3.
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4
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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, 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, 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
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OFFSET
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1,5
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LINKS
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FORMULA
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EXAMPLE
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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.
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MATHEMATICA
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Accumulate[Table[If[PrimeQ[n]&&Mod[n, 3]==2, 1, 0], {n, 90}]] (* Harvey P. Dale, May 12 2022 *)
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PROG
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(PARI) a(n) = sum(i=1, n, isprime(i) && (i%3==2))
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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