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A119584
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Sum{k=1 to phi(n)-1} t(n,k)*t(n,k+1), where t(n,k) is the k-th positive integer which is coprime to n and phi(n) is the number of positive integers which are <= n and are coprime to n.
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0
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0, 0, 2, 3, 20, 5, 70, 53, 121, 87, 330, 117, 572, 305, 507, 553, 1360, 481, 1938, 873, 1586, 1405, 3542, 1241, 3846, 2415, 4006, 2765, 7308, 1875, 8990, 4945, 6828, 5675, 9333, 4525, 15540, 8053, 11567, 7745, 21320, 6047, 24682, 12005, 15244, 14625
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OFFSET
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1,3
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COMMENTS
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All primes are records and there exists records which are not primes, but they are rare (see A120033). - Robert G. Wilson v, Jun 05 2006
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LINKS
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Table of n, a(n) for n=1..46.
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EXAMPLE
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The positive integers which are <= 8 and are coprime to 8 are 1, 3, 5 and 7. So a(8) = 1*3 + 3*5 + 5*7 = 53.
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MATHEMATICA
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f[n_] := Block[{s = Select[ Range@n, GCD[ #, n] == 1 &]}, Plus @@ (Most@s*Rest@s)]; Array[f, 46] - Robert G. Wilson v, Jun 05 2006
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CROSSREFS
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Sequence in context: A038584 A108022 A108884 * A089181 A028425 A224987
Adjacent sequences: A119581 A119582 A119583 * A119585 A119586 A119587
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet May 31 2006
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EXTENSIONS
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More terms from Robert G. Wilson v, Jun 05 2006
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STATUS
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approved
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