%I A007503 M1321
%S A007503 2,5,6,10,8,16,10,19,16,22,14,34,16,28,28,36,20,45,22,48,
%T A007503 36,40,26,68,34,46,44,62,32,80,34,69,52,58,52,100,40,64,60,
%U A007503 98,44,104,46,90,84,76,50,134,60,99,76,104,56,128,76,128
%N A007503 Number of subgroups of dihedral group: sigma(n)+d(n).
%D A007503 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A007503 David W. Jensen and Eric R. Bussian, A Number-Theoretic Approach to Counting 
               Subgroups of Dihedral Groups, Two-Year College Math. Jnl., 23 (1992), 
               150-152.
%H A007503 T. D. Noe, <a href="b007503.txt">Table of n, a(n) for n = 1..1000</a>
%F A007503 G.f.: sum(k>=1, 1/(1-x^k)^2) - Benoit Cloitre (benoit7848c(AT)orange.fr), 
               Apr 21 2003
%F A007503 G.f.: sum(i=1, oo, (1+i)/(1-x^i)) - Jon Perry (perry(AT)globalnet.co.uk), 
               Jul 03 2004
%p A007503 with(numtheory): seq(sigma(n)+tau(n), n=1..56) ; - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), 
               Jun 04 2008
%Y A007503 Sequence in context: A051677 A122965 A054463 this_sequence A112967 A109150 
               A004202
%Y A007503 Adjacent sequences: A007500 A007501 A007502 this_sequence A007504 A007505 
               A007506
%K A007503 nonn
%O A007503 1,1
%A A007503 N. J. A. Sloane (njas(AT)research.att.com), Robert G. Wilson v (rgwv(AT)rgwv.com)