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Search: id:A063770
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| A063770 |
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Numbers n such that Sum_{k=1..n} sigma(k) divides Prod_{k=1..n} phi(k). |
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+0
1
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| 1, 28, 52, 53, 55, 63, 76, 159, 166, 176, 219, 230, 289, 302, 303, 318, 321, 327, 348, 360, 364, 365, 381, 383, 402, 417, 430, 434, 438, 444, 451, 452, 454, 465, 469, 478, 504, 512, 522, 530, 531, 557, 559, 570, 572, 584, 595, 613, 629, 631, 641, 645, 684
(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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PROGRAM
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(PARI) j=[]; for(n=1, 1300, a=sum(k=1, n, sigma(k)); b=prod(k=1, n, eulerphi(k)); if(Mod(b, a)==0, j=concat(j, n))); j
(PARI) { n=0; s=0; p=1; for (m=1, 10^9, s+=sigma(m); p*=eulerphi(m); if(p%s == 0, write("b063770.txt", n++, " ", m); if (n==1000, break)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Aug 30 2009]
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CROSSREFS
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Sequence in context: A156719 A039615 A046419 this_sequence A161923 A039772 A043134
Adjacent sequences: A063767 A063768 A063769 this_sequence A063771 A063772 A063773
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KEYWORD
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nonn
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AUTHOR
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Jason Earls (zevi_35711(AT)yahoo.com), Aug 15 2001
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