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A093074
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Greatest prime factor of n and its direct neighbors.
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8
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2, 3, 3, 5, 5, 7, 7, 7, 5, 11, 11, 13, 13, 13, 7, 17, 17, 19, 19, 19, 11, 23, 23, 23, 13, 13, 13, 29, 29, 31, 31, 31, 17, 17, 17, 37, 37, 37, 19, 41, 41, 43, 43, 43, 23, 47, 47, 47, 7, 17, 17, 53, 53, 53, 11, 19, 29, 59, 59, 61, 61, 61, 31, 13, 13, 67, 67, 67, 23, 71, 71, 73
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OFFSET
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1,1
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COMMENTS
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for all primes p>2: a(p)=a(p-1)=p and if p is not the lesser member of a twin prime pair, then also a(p+1)=p;
(n,n+2) is a twin prime pair iff a(n-1)=a(n)=n and a(n+1)=a(n+2)=a(n+3)=n+2.
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LINKS
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FORMULA
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PROG
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(Haskell)
a093074 1 = 2
a093074 n = maximum $ map a006530 [n-1..n+1]
(PARI) a(n)=my(p=precprime(n+1)); if(p>n-2, p, vecmax(apply(n->vecmax(factor(n)[, 1]), [n-1, n, n+1]))) \\ Charles R Greathouse IV, Feb 19 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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