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Search: id:A058026
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| A058026 |
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Number of positive integers, k, where k <= n and GCD(k,n) = GCD(k+1,n) = 1. |
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4
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| 1, 0, 1, 0, 3, 0, 5, 0, 3, 0, 9, 0, 11, 0, 3, 0, 15, 0, 17, 0, 5, 0, 21, 0, 15, 0, 9, 0, 27, 0, 29, 0, 9, 0, 15, 0, 35, 0, 11, 0, 39, 0, 41, 0, 9, 0, 45, 0, 35, 0, 15, 0, 51, 0, 27, 0, 17, 0, 57, 0, 59, 0, 15, 0, 33, 0, 65, 0, 21, 0, 69, 0, 71, 0, 15, 0, 45, 0, 77, 0, 27, 0, 81, 0, 45, 0, 27, 0
(list; graph; listen)
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OFFSET
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1,5
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FORMULA
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Multiplicative with a(p^e) = p^(e-1)*(p-2). - Vladeta Jovovic (vladeta(AT)Eunet.yu), Dec 01 2001
Sum_{d|n} n/d*mu(d)*tau(d). - Vladeta Jovovic (vladeta(AT)Eunet.yu), Apr 29 2002
a(n) = Sum_{d divides n} phi(n/d)*(-1)^omega(d). - Vladeta Jovovic (vladeta(AT)Eunet.yu), Sep 26 2002
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EXAMPLE
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a(15) = 3 because 1 and 2, 7 and 8, and 13 and 14 are all relatively prime to 15.
a(15) = a(3*5) = a(3)*a(5) = 3^0*(3-2)*5^0*(5-2) = 3.
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CROSSREFS
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Cf. A070554, A069828.
Adjacent sequences: A058023 A058024 A058025 this_sequence A058027 A058028 A058029
Sequence in context: A122274 A003966 A123931 this_sequence A004605 A086664 A109753
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KEYWORD
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nonn,mult
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AUTHOR
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Leroy Quet (qq-quet(AT)mindspring.com), Nov 15 2000
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