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Search: id:A089496
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| A089496 |
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mu(prime(n)+1) + mu(prime(n)-1), where mu is the Moebius function. |
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+0
4
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| -1, 1, 1, 1, 1, 0, 0, 1, -1, -1, 1, -1, -1, 1, 0, 1, 1, -1, -1, 1, -1, 1, 0, 0, -1, -1, 1, -1, -1, 0, -1, -1, -1, 0, 0, 1, 0, 1, -1, 1, -1, -1, 1, 0, 0, 1, -1, 1, -1, 0, -1, 0, 0, -1, 1, 0, 0, 1, -1, -1, 0, 0, -1, 1, -1, 1, 0, 1, 0, -1, 1, -1, -1, 0, 1, 1, 1, -1, -1, -1, 1, -1, -1, -1, -1, 0, 1, 1, 1, 1, 1, 0, 0, -1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, -1
(list; graph; listen)
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OFFSET
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2,1
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COMMENT
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This sum is always -1, 0 or 1 because for odd prime p, both p-1 and p+1 cannot be square-free; one of them will be divisible by 4. This also implies that terms in this sequence are zero only for primes p such that mu(p-1) = mu(p+1) = 0, which is A075432.
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LINKS
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Eric Weisstein's World of Mathematics, Moebius Function
Eric Weisstein's World of Mathematics, Legendre Symbol
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FORMULA
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Let p = prime(n), then a(n) = mu(p+(-1/p)), where (-1/p) is the Legendre symbol, A070750. (Pieter Moree)
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MATHEMATICA
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Table[MoebiusMu[Prime[n]+1] + MoebiusMu[Prime[n]-1], {n, 2, 150}]
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CROSSREFS
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Cf. A089451 (mu(p-1) for prime p), A089495 (mu(p+1) for prime p), A089497 (mu(p+1)-mu(p-1) for prime p).
Sequence in context: A014044 A014079 A089497 this_sequence A114592 A118110 A131522
Adjacent sequences: A089493 A089494 A089495 this_sequence A089497 A089498 A089499
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KEYWORD
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sign
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AUTHOR
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T. D. Noe (noe(AT)sspectra.com), Nov 04 2003
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