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Search: id:A065093
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| 1, 2, 5, 8, 16, 20, 36, 44, 68, 76, 120, 124, 188, 196, 276, 272, 404, 380, 544, 532, 716, 668, 968, 860, 1184, 1120, 1472, 1332, 1896, 1624, 2204, 2036, 2656, 2352, 3284, 2752, 3684, 3356, 4324, 3744, 5192, 4312, 5720, 5180, 6540, 5628, 7768, 6388, 8476
(list; graph; listen)
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OFFSET
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1,2
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LINKS
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Harry J. Smith, Table of n, a(n) for n=1,...,1000
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FORMULA
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Sum_{k=1..n} phi(k)*phi(n+1-k), where phi is Euler totient function (A000010).
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PROGRAM
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(PARI) { for (n=1, 1000, a=sum(k=1, n, eulerphi(k)*eulerphi(n+1-k)); write("b065093.txt", n, " ", a) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Oct 06 2009]
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CROSSREFS
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Cf. A000385, A055507.
Sequence in context: A081660 A065618 A080084 this_sequence A129299 A096541 A137685
Adjacent sequences: A065090 A065091 A065092 this_sequence A065094 A065095 A065096
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KEYWORD
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easy,nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)eunet.rs), Nov 11 2001
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