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A000694 Related to population of numbers of form x^2 + y^2.
(Formerly M1021 N0384)
0

%I M1021 N0384

%S 1,2,4,6,11,19,34,63,117,218,411,780,1487,2849,5477,10562,20419,39563,

%T 76805,149360,290896,567321,1107775,2165487,4237384,8299283,16268639,

%U 31915437,62656158,123088460,241958676,475901501,936544684

%N Related to population of numbers of form x^2 + y^2.

%C Shanks' paper gives erroneous value a(16)=10555. - _Sean A. Irvine_, Feb 25 2011

%D N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H D. Shanks, <a href="http://dx.doi.org/10.1090/S0025-5718-1964-0159174-9">The second-order term in the asymptotic expansion of B(x)</a>, Mathematics of Computation 18 (1964), pp. 75-86.

%H <a href="/index/Qua#quadpop">Index entries for sequences related to populations of quadratic forms</a>

%p Digits:=500;

%p K:=.764223653589220662990698731250092328116790541393409514721686673

%p 7496146416587328588384015050131312337219372691207925926341874206467

%p 8084323063315434629380531605171169636177508819961243824994277683469

%p 0516235139218719620569053295644670419176349770659569905712938660289

%p 3858998296105166296089099177929836072973697200640316985128636517347

%p 3921065768550978681981674707359066921;

%p a:=n->round(evalf((2/3)*K*int(1/sqrt(ln(t)), t=1..2^n)));

%p # _Sean A. Irvine_, Feb 25 2011

%Y Cf. A000691.

%K nonn

%O 1,2

%A _N. J. A. Sloane_

%E More terms from _Sean A. Irvine_, Feb 24 2011

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Last modified February 17 20:01 EST 2018. Contains 299296 sequences. (Running on oeis4.)