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Search: id:A065572
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| A065572 |
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Composite n such that phi(n) = phi(n-1) + phi(n-2). |
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+0
3
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| 1037, 1541, 6527, 9179, 55387, 61133, 72581, 110177, 152651, 179297, 244967, 299651, 603461, 619697, 1876727, 2841917, 3058211, 3971321, 4110653, 4316441, 4397317, 6008861
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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619697=13*73*653 is the smallest solution not of the form p or pq for distinct primes p and q.
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LINKS
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Harry J. Smith, Table of n, a(n) for n=1,...,50
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MATHEMATICA
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Select[ Range[3, 10^7], !PrimeQ[ # ] && EulerPhi[ # ] == EulerPhi[ # - 1] + EulerPhi[ # - 2] & ]
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PROGRAM
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(PARI) { n=0; e1=eulerphi(2); e2=eulerphi(1); for (m=3, 10^9, e=eulerphi(m); if (!isprime(m) && e==e2 + e1, write("b065572.txt", n++, " ", m); if (n==100, return)); e2=e1; e1=e ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Oct 23 2009]
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CROSSREFS
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Cf. A065557 (includes prime solutions)
Sequence in context: A043388 A163559 A159052 this_sequence A074673 A020395 A069456
Adjacent sequences: A065569 A065570 A065571 this_sequence A065573 A065574 A065575
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KEYWORD
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nonn
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AUTHOR
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Len Smiley (smiley(AT)math.uaa.alaska.edu) and Robert G. Wilson v (rgwv(AT)rgwv.com), Nov 30 2001
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