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A267134
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a(n) = n minus the number of primes of form 6m + 1 that are less than n-th prime of form 6m - 1.
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0
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1, 1, 1, 1, 2, 1, 1, 2, 3, 2, 1, 2, 2, 2, 2, 2, 3, 3, 1, 2, 3, 3, 3, 1, 1, 2, 2, 3, 4, 5, 4, 4, 4, 4, 3, 3, 4, 2, 3, 3, 3, 3, 2, 3, 3, 3, 4, 4, 4, 5, 6, 4, 5, 6, 5, 6, 7, 5, 4, 4, 5, 6, 5, 6, 6, 6, 4, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 6, 6, 7, 8, 6, 7, 7, 6, 6, 4, 4, 5, 6, 4, 4, 4, 5, 6
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OFFSET
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1,5
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LINKS
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EXAMPLE
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a(5) = 2 because the fifth prime of the form 6m - 1 is 29, there are three primes of the form 6m + 1 less than 29 (namely 7, 13, 19) and 5 - 3 = 2.
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MATHEMATICA
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s = Prime@Range@120 /. p_ /; Mod[p, 6] != 5 -> Nothing; Table[n - Count[Flatten@ Prime@ Range@ PrimePi@ Take[s, {n}], p_ /; Mod[p, 6] == 1], {n, 120}] (* Michael De Vlieger, Feb 10 2016 *)
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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