Search: id:A000691
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%I A000691 M0713 N0263
%S A000691 1,2,3,5,9,16,29,52,94,175,327,616,1169,2231,4273,8215,15842,30628,
%T A000691 59345,115208,224040,436343,850981,1661663,3248231,6356076,12448925,
%U A000691 24402959,47873156,93984236,184632691,362938014,713852258,1404817021
%N A000691 Ramanujan's approximation to population of x^2 + y^2.
%D A000691 D. Shanks, The second-order term in the asymptotic expansion of B(x), 
               Math. Comp., 18 (1964), 75-86.
%D A000691 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A000691 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%H A000691 <a href="Sindx_Qua.html#quadpop">Index entries for sequences related 
               to populations of quadratic forms</a>
%p A000691 K:=.764223653589220662990698731250092328116790541393409514721686673\
%p A000691 7496146416587328588384015050131312337219372691207925926341874206467\
%p A000691 8084323063315434629380531605171169636177508819961243824994277683469\
%p A000691 0516235139218719620569053295644670419176349770659569905712938660289\
%p A000691 3858998296105166296089099177929836072973697200640316985128636517347\
%p A000691 3921065768550978681981674707359066921; a:=n->round(evalf(K*int(1/sqrt(ln(t)),
               t=1..2^n)));
%Y A000691 Sequence in context: A006788 A054650 A022857 this_sequence A103285 A000049 
               A000050
%Y A000691 Adjacent sequences: A000688 A000689 A000690 this_sequence A000692 A000693 
               A000694
%K A000691 nonn
%O A000691 0,2
%A A000691 N. J. A. Sloane (njas(AT)research.att.com).
%E A000691 More terms and Maple program from Salvador Perez (pies314(AT)hotmail.com), 
               May 08 2005

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