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A029704 Q(sqrt(n)) has class number 4. 4

%I

%S 82,130,145,170,195,210,219,231,255,274,290,291,322,323,330,370,390,

%T 410,434,435,438,445,455,462,483,505,510,514,530,546,555,570,579,582,

%U 595,610,615,626,627,651,658,663,674,689,690,706,714,715,723,731,754,759,770

%N Q(sqrt(n)) has class number 4.

%H Charles R Greathouse IV, <a href="/A029704/b029704.txt">Table of n, a(n) for n = 1..10000</a>

%H <a href="/index/Qua#quadfield">Index entries for sequences related to quadratic fields</a>

%t Select[Range[770], SquareFreeQ[#] && NumberFieldClassNumber@Sqrt[#] == 4 &] (* _Arkadiusz Wesolowski_, Oct 18 2012 *)

%o (PARI) is(n)=if(issquarefree(n), my(c=bnfinit('x^2-n).cyc); c==[4] || c==[2,2], 0) \\ _Charles R Greathouse IV_, Oct 18 2012

%Y Cf. A003172, A029702-A029703, A029705, A218038-A218042.

%K nonn

%O 1,1

%A Paolo Dominici (pl.dm(AT)libero.it)

%E Initial term added by _Arkadiusz Wesolowski_, Oct 18 2012

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Last modified October 21 08:16 EDT 2019. Contains 328292 sequences. (Running on oeis4.)