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A076472
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Number of pairs (p,q) of successive primes with p+q<=n and gcd(p+q,n)>1.
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2
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0, 0, 0, 0, 1, 0, 0, 1, 0, 2, 0, 2, 0, 2, 2, 2, 0, 3, 0, 4, 2, 3, 0, 4, 1, 4, 3, 4, 0, 6, 0, 5, 4, 5, 2, 6, 0, 6, 5, 7, 0, 7, 0, 7, 7, 7, 0, 7, 1, 8, 6, 8, 0, 8, 2, 8, 6, 8, 0, 10, 0, 9, 7, 9, 4, 9, 0, 10, 7, 11, 0, 10, 0, 10, 8, 10, 1, 11, 0, 12, 8, 11, 0, 12, 4, 12, 9, 12, 0, 14, 4, 13, 10, 13, 4, 13
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,10
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COMMENTS
| a(n) = A076471(n) - A076473(n);
for n>6: a(n)=0 iff n is prime.
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EXAMPLE
| n=27: gcd(2+3,27)=1, gcd(3+5,27)=1, gcd(5+7,27)=3, gcd(7+11,27)=9, gcd(11+13,27)=3, hence a(27)=3.
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CROSSREFS
| Sequence in context: A039979 A204173 A103668 * A161840 A140302 A085341
Adjacent sequences: A076469 A076470 A076471 * A076473 A076474 A076475
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KEYWORD
| nonn
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Oct 14 2002
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