A218040 -id:A218040 - cp's OEIS frontend

A218039 Numbers n such that Q(sqrt(n)) has class number 7.

577, 1009, 1087, 1294, 1601, 1761, 1934, 2029, 2251, 2302, 2467, 2913, 4139, 4229, 4702, 5039, 5273, 5417, 5743, 5827, 6151, 6598, 7919, 8097, 8311, 8462, 8661, 8773, 9029, 9049, 9101, 9289, 9326, 9539, 10117, 10313, 10357, 10713, 10957, 11021, 11053, 11269

Offset: 1

Arkadiusz Wesolowski, Oct 19 2012

nonn

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Class Number

Cf. A003172, A029702-A029705, A218038, A218040-A218042.

Select[Range[11269], SquareFreeQ[#] && NumberFieldClassNumber@Sqrt[#] == 7 &]

is(n)=issquarefree(n) && qfbclassno(if(n%4>1,4,1)*n)==7 \\ Charles R Greathouse IV, Jan 19 2017

A218041 Numbers n such that Q(sqrt(n)) has class number 9.

Original entry on oeis.org

1129, 1654, 3137, 3719, 4409, 4534, 5521, 5623, 5878, 6809, 7573, 7873, 9998, 10273, 10721, 10814, 11027, 11641, 12323, 12409, 12657, 13069, 13691, 14159, 15374, 15629, 16321, 16382, 17273, 17989, 18633, 19441, 21023, 21781, 22497, 22502, 23003, 23806

Offset: 1

Arkadiusz Wesolowski, Oct 19 2012

nonn

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Class Number

Cf. A003172, A029702-A029705, A218038-A218040, A218042.

Select[Range[23806], SquareFreeQ[#] && NumberFieldClassNumber@Sqrt[#] == 9 &]

is(n)=issquarefree(n) && qfbclassno(if(n%4>1,4,1)*n)==9 \\ Charles R Greathouse IV, Jan 19 2017

A081363 Smallest squarefree integer k such that Q(sqrt(k)) has class number n.

Original entry on oeis.org

2, 10, 79, 82, 401, 235, 577, 226, 1129, 1111, 1297, 730, 4759, 1534, 9871, 2305, 7054, 4954, 15409, 3601, 7057, 4762, 23593, 9634, 24859, 13321, 8761, 5626, 49281, 11665, 97753, 15130, 55339, 19882, 25601, 18226, 24337, 19834, 41614, 16899, 55966, 47959

Offset: 1

Dean Hickerson, Mar 19 2003

nonn

What is known about the asymptotics of this sequence? - Charles R Greathouse IV, Jan 26 2017

Records: 2, 10, 79, 82, 401, 577, 1129, 1297, 4759, 9871, 15409, 23593, 24859, 49281, 97753, 106537, 159199, 197137, 212137, 239119, 245023, 444089, 589822, 614849, 815413, 837929, 943951, 1025494, 1224121, 1240369, 1333255, 1334026, ..., . - Robert G. Wilson v, Apr 12 2017

Robert G. Wilson v, Table of n, a(n) for n = 1..214

Cf. A081319, A081364, A094619, A094612, A094613, A094614.

Cf. A219361, A029702, A029703, A029704, A029705, A218038, A218039, A218040, A218041, A218042, A276541. - Robert G. Wilson v, Apr 12 2017

t[] := 0; k = 2; While[k < 56000, cn = NumberFieldClassNumber@Sqrt@k; If[ t[cn] == 0, t[cn] = k; Print[{cn, k}]]; k++]; t@# & /@ Range@ 42 (* _Robert G. Wilson v, Apr 12 2017 *)

v=vector(100); for(n=2,1e6, if(!issquarefree(n), next); t=qfbclassno(if(n%4>1,4*n,n)); if(t<=#v && v[t]==0, v[t]=n; print("a("t") = "n))) \\ Charles R Greathouse IV, Jan 26 2017

More terms from Max Alekseyev, Apr 28 2010

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A218039 Numbers n such that Q(sqrt(n)) has class number 7.

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A218041 Numbers n such that Q(sqrt(n)) has class number 9.

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A081363 Smallest squarefree integer k such that Q(sqrt(k)) has class number n.

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