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 A029703 Q(sqrt(n)) has class number 3. 4
 79, 142, 223, 229, 254, 257, 321, 326, 359, 443, 469, 473, 659, 733, 761, 839, 934, 993, 1091, 1101, 1171, 1223, 1229, 1257, 1367, 1373, 1478, 1489, 1509, 1523, 1567, 1627, 1646, 1787, 1811, 1847, 1901, 1907, 1929, 1957, 1987, 2021, 2089, 2099, 2101, 2143, 2177, 2207, 2213 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 EXAMPLE 79 is in the sequence because Z[sqrt(79)] has class number 3. Z[sqrt(82)] has class number 4 and therefore 82 is not in the sequence. MATHEMATICA Select[Range[2000], SquareFreeQ[#] && NumberFieldClassNumber[Sqrt[#]] == 3 &] (* Alonso del Arte, Oct 17 2012 *) PROG (PARI) A007947(n)={my(p); p=factor(n)[, 1]; prod(i=1, length(p), p[i]); } { for (n=2, 10^4,     if ( n!=A007947(n), next() );     K = bnfinit(x^2 - n);     if ( K.cyc == [3], print1( n, ", ") ); ); } /* Joerg Arndt, Oct 18 2012 */ CROSSREFS Cf. A003172, A029702, A029704-A029705, A218038-A218042. Sequence in context: A141997 A107184 A250658 * A142082 A031890 A140008 Adjacent sequences:  A029700 A029701 A029702 * A029704 A029705 A029706 KEYWORD nonn AUTHOR Paolo Dominici (pl.dm(AT)libero.it) EXTENSIONS Missing initial term (79) added by Alonso del Arte, Oct 17 2012 STATUS approved

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Last modified October 17 08:36 EDT 2019. Contains 328107 sequences. (Running on oeis4.)