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Search: id:A129950
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| A129950 |
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Characteristic function of twin primes: 1 if twin prime member, 0 if isolated prime or -1 if not prime. |
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+0
1
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| 0, -1, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, -1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, -1, 0, 0, 0, 1, 0, 1, 0, 0, 0, -1, 0, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, -1, 0, 0, 0, -1, 0, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, 0, -1, 0, 0, 0
(list; graph; listen)
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OFFSET
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1,1
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PROGRAM
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(PARI) for(j=1, 100, print1(t(j)", ")) t(x) = if(abs(istwin(x))==1||x==5, 1, if(isprime(x), -1, 0)) istwin(n) = local(p1, p2); if(n==5, return(2)); if(isprime(n), p1=n-2; p2=n+2; if(isprime(p1), return(1)); if(isprime(p2), return(-1)); return(0))
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CROSSREFS
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Adjacent sequences: A129947 A129948 A129949 this_sequence A129951 A129952 A129953
Sequence in context: A010060 A118247 A122257 this_sequence A010051 A131929 A100821
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KEYWORD
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sign
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AUTHOR
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Cino Hilliard (hillcino368(AT)hotmail.com), Jun 10 2007
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