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A071838
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Pi(8,3)(n) + Pi(8,5)(n) - Pi(8,1)(n) - Pi(8,7)(n) where Pi(a,b)(x) denotes the number of primes in the arithmetic progression ak+b less than or equal to x.
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0
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0, 0, 1, 1, 2, 2, 1, 1, 1, 1, 2, 2, 3, 3, 3, 3, 2, 2, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2, 3, 3, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 2, 2, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 5, 5, 4, 4, 4, 4, 4, 4, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 3, 3, 3, 3, 3, 3, 3, 3, 2, 2, 2, 2, 3, 3, 2, 2, 2
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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COMMENTS
| Although the initial terms are nonnegative, infinitely many terms should be negative. For which n does a(n)=-1 ?
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PROG
| (PARI) for(n=1, 200, print1(sum(i=1, n, if((i*isprime(i)-3)%8, 0, 1)+if((i*isprime(i)-5)%8, 0, 1))-if((i*isprime(i)-1)%8, 0, 1))-if((i*isprime(i)-7)%8, 0, 1)), ", "))
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CROSSREFS
| Cf. A066520.
Sequence in context: A101615 A140193 A073741 * A157896 A156072 A165031
Adjacent sequences: A071835 A071836 A071837 * A071839 A071840 A071841
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KEYWORD
| easy,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Jun 08 2002
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