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Search: id:A015613
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| A015613 |
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a(n)=sum(i=1,n,eulerphi(i)*ceil(n/i))-sum(i=1,n,eulerphi(i)*floor(n/i)). |
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+0
1
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| 0, 0, 1, 2, 5, 6, 11, 14, 19, 22, 31, 34, 45, 50, 57, 64, 79, 84, 101, 108, 119, 128, 149, 156, 175, 186, 203, 214, 241, 248, 277, 292, 311, 326, 349, 360, 395, 412, 435, 450, 489, 500, 541, 560, 583, 604, 649, 664, 705, 724, 755, 778, 829, 846, 885, 908, 943
(list; graph; listen)
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OFFSET
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1,4
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FORMULA
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a(n) = sum of phi(e) where e ranges over all non-divisors of n that are between 1 and n. - Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Oct 24 2002
a(n) = A002088(n) - n.
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MATHEMATICA
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f[n_] := Module[{s, i}, s = 0; For[i = 1, i < n, i++, If[Mod[n, i] != 0, s = s + EulerPhi[i]]]; s]; Table[f[i], {i, 1, 100}]
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CROSSREFS
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Sequence in context: A092306 A090552 A024520 this_sequence A135013 A103035 A088273
Adjacent sequences: A015610 A015611 A015612 this_sequence A015614 A015615 A015616
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KEYWORD
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nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Oct 24 2002
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EXTENSIONS
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Edited by Vladeta Jovovic (vladeta(AT)Eunet.yu), Mar 23 2003
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