Search: id:A065572
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%I A065572
%S A065572 1037,1541,6527,9179,55387,61133,72581,110177,152651,179297,244967,
%T A065572 299651,603461,619697,1876727,2841917,3058211,3971321,4110653,4316441,
%U A065572 4397317,6008861
%N A065572 Composite n such that phi(n) = phi(n-1) + phi(n-2).
%C A065572 619697=13*73*653 is the smallest solution not of the form p or pq for 
               distinct primes p and q.
%H A065572 Harry J. Smith, <a href="b065572.txt">Table of n, a(n) for n=1,...,50</
               a>
%t A065572 Select[ Range[3, 10^7], !PrimeQ[ # ] && EulerPhi[ # ] == EulerPhi[ # 
               - 1] + EulerPhi[ # - 2] & ]
%o A065572 (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]
%Y A065572 Cf. A065557 (includes prime solutions)
%Y A065572 Sequence in context: A043388 A163559 A159052 this_sequence A074673 A020395 
               A069456
%Y A065572 Adjacent sequences: A065569 A065570 A065571 this_sequence A065573 A065574 
               A065575
%K A065572 nonn
%O A065572 1,1
%A A065572 Len Smiley (smiley(AT)math.uaa.alaska.edu) and Robert G. Wilson v (rgwv(AT)rgwv.com), 
               Nov 30 2001

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