Search: id:A062011
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%I A062011
%S A062011 2,4,4,6,4,8,4,8,6,8,4,12,4,8,8,10,4,12,4,12,8,8,4,16,6,8,8,12,4,16,4,
%T A062011 12,8,8,8,18,4,8,8,16,4,16,4,12,12,8,4,20,6,12,8,12,4,16,8,16,8,8,4,24,
%U A062011 4,8,12,14,8,16,4,12,8,16,4,24,4,8,12,12,8,16,4,20,10,8,4,24,8,8,8,16
%N A062011 Number of cyclic subgroups of the group C_n X C_2 (where C_n is the cyclic 
               group with n elements).
%C A062011 Also number of divisors of p*n, where p is any prime not dividing n, 
               e.g.: a(n) = A000005(A087560(n)) = A000005(A119416(n)). - Reinhard 
               Zumkeller (reinhard.zumkeller(AT)gmail.com), May 17 2006
%H A062011 Harry J. Smith, <a href="b062011.txt">Table of n, a(n) for n=1,...,1000</
               a>
%F A062011 a(n) = 2*tau(n).
%F A062011 More generally, the number of cyclic subgroups of the group C_n X C_m 
               is Sum_{i|n, j|m} phi(i)*phi(j)/phi(lcm(i, j)), where phi=Euler totient 
               function, cf. A000010. - Vladeta Jovovic (vladeta(AT)eunet.rs), Jul 
               15 2001
%o A062011 (PARI) { for (n=1, 1000, write("b062011.txt", n, " ", 2*numdiv(n)) ) 
               } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jul 29 2009]
%Y A062011 Cf. A060710, A000005, A060648.
%Y A062011 Sequence in context: A049782 A091666 A084290 this_sequence A132857 A152782 
               A057696
%Y A062011 Adjacent sequences: A062008 A062009 A062010 this_sequence A062012 A062013 
               A062014
%K A062011 nonn,easy
%O A062011 1,1
%A A062011 Ahmed Fares (ahmedfares(AT)my-deja.com), Jul 12 2001
%E A062011 More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Jul 14 2001

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