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A011755
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Sum{k=1..n} k*phi(k).
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0
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1, 3, 9, 17, 37, 49, 91, 123, 177, 217, 327, 375, 531, 615, 735, 863, 1135, 1243, 1585, 1745, 1997, 2217, 2723, 2915, 3415, 3727, 4213, 4549, 5361, 5601, 6531, 7043, 7703, 8247, 9087, 9519, 10851, 11535, 12471, 13111, 14751, 15255, 17061, 17941, 19021, 20033
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| a(n) = Sum_{(x,y): 1<=x<=y<=n, 1=gcd(x,y)} y. Sum_{(x,y): 1<=x<=y<=n, 1=gcd(x,y)} x = (a(n)+1)/2. - Vladeta Jovovic (vladeta(AT)eunet.rs), Jan 02 2003
Equals row sums of triangle A110663. Example: a(4) = 17 = (6 + 5 + 4 + 2), where row 4 of triangle A110663 = (6, 5, 4, 2). - Gary W. Adamson (qntmpkt(AT)yahoo.com), Jul 26 2008
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FORMULA
| Asymptotically : a(n)=C*n^3 with C=0.2026437... - Benoit Cloitre (benoit7848c(AT)orange.fr), Jan 14 2002
Asymptotically: a(n) ~ 2/Pi^2*n^3. - Vladeta Jovovic (vladeta(AT)eunet.rs), Jan 02 2003
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CROSSREFS
| Cf. A000010, A002088. Partial sums of A002618.
Cf. A110663.
Sequence in context: A049778 A123325 A116688 * A128301 A176148 A206701
Adjacent sequences: A011752 A011753 A011754 * A011756 A011757 A011758
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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