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Search: id:A064951
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| A064951 |
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Sum of LCM(x, y) for 1 <= x, y <= n. |
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+0
2
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| 1, 7, 28, 72, 177, 303, 604, 948, 1497, 2127, 3348, 4272, 6313, 8119, 10324, 13060, 17701, 20995, 27512, 32132, 38453, 45779, 57440, 64664, 77689, 89935, 104704, 117948, 141525, 154755, 183616, 205472, 231113, 258959, 290564, 314720, 364041
(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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a(n) = a(n-1)+2*A051193(n)-n = a(n-1)+n*A057660(n) = sum_i, j{1<= i<= j<= n}[j^2/gcd(i, j)]. - Henry Bottomley (se16(AT)btinternet.com), Oct 29 2001
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PROGRAM
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(PARI) { a=0; for (n=1, 1000, a+=n*sum(k=1, n, n/gcd(n, k)); write("b064951.txt", n, " ", a) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Oct 01 2009]
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CROSSREFS
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Cf. A018806.
Sequence in context: A033582 A008457 A138503 this_sequence A073995 A061968 A024012
Adjacent sequences: A064948 A064949 A064950 this_sequence A064952 A064953 A064954
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KEYWORD
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nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)eunet.rs), Oct 28 2001
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