A094619 -id:A094619 - cp's OEIS frontend

A218159 Fundamental discriminants of real quadratic number fields with class number 9.

1129, 3137, 4409, 5521, 6616, 6809, 7573, 7873, 10273, 10721, 11641, 12409, 12657, 13069, 14876, 15629, 16321, 17273, 17989, 18136, 18633, 19441, 21781, 22492, 22497, 23512, 24029, 24169, 24697, 24781, 25361, 26573, 27221, 27349, 28901, 29317, 31897

Offset: 1

Arkadiusz Wesolowski, Oct 22 2012

nonn

Eric Weisstein's World of Mathematics, Class Number
Index entries for sequences related to quadratic fields

Cf. A003656, A094619, A094612-A094614, A218156-A218158, A218160.

Select[Range[31897], NumberFieldDiscriminant@Sqrt[#] == # && NumberFieldClassNumber@Sqrt[#] == 9 &]

A344408 Positive discriminants of orders with class number 2.

Original entry on oeis.org

40, 60, 65, 85, 96, 104, 105, 120, 136, 140, 156, 160, 165, 168, 185, 192, 200, 204, 205, 220, 221, 224, 232, 240, 252, 260, 264, 265, 273, 280, 285, 288, 296, 300, 305, 312, 320, 325, 336, 340, 345, 348, 352, 357, 360, 364, 365, 377, 380, 384, 385, 408

Offset: 1

Jianing Song, May 17 2021

nonn

Also positive discriminants of orders with class group isomorphic to C_2.

The fundamental terms are listed in A094619.

Jianing Song, Table of n, a(n) for n = 1..10001

Cf. A133315 (positive discriminants of orders with class number 1), this sequence (class number 2), A344409 (class number 3).

Cf. A322710 (the negative discriminant case), A094619.

isA344408(d) = (d>0) && !issquare(d) && ((d%4==0)||(d%4==1)) && quadclassunit(d)[2]==[2]

cp's OEIS Frontend

A218159 Fundamental discriminants of real quadratic number fields with class number 9.

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