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A000414 Numbers that are the sum of 4 nonzero squares. 11

%I

%S 4,7,10,12,13,15,16,18,19,20,21,22,23,25,26,27,28,30,31,33,34,35,36,

%T 37,38,39,40,42,43,44,45,46,47,48,49,50,51,52,53,54,55,57,58,59,60,61,

%U 62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81

%N Numbers that are the sum of 4 nonzero squares.

%H T. D. Noe, <a href="/A000414/b000414.txt">Table of n, a(n) for n = 1..1000</a>

%H <a href="/index/Su#ssq">Index entries for sequences related to sums of squares</a>

%F a(n) = n + O(log n). - _Charles R Greathouse IV_, Sep 03 2014

%t q=16;lst={};Do[Do[Do[Do[z=a^2+b^2+c^2+d^2;If[z<=(q^2)+3,AppendTo[lst,z]],{d,q}],{c,q}],{b,q}],{a,q}];Union@lst (*_Vladimir Joseph Stephan Orlovsky_, Feb 07 2010 *)

%o (PARI) is(n)=my(k=if(n,n/4^valuation(n,4),2)); k!=2 && k!=6 && k!=14 && !setsearch([0, 1, 3, 5, 9, 11, 17, 29, 41], n) \\ _Charles R Greathouse IV_, Sep 03 2014

%Y Cf. A000534 (complement).

%K nonn

%O 1,1

%A _N. J. A. Sloane_ and _J. H. Conway_

%E corrected 6/95

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Last modified July 11 23:53 EDT 2020. Contains 335654 sequences. (Running on oeis4.)