A390357 a(n) is the number of imaginary biquadratic fields with class number 2*n.

160, 408, 552, 1186, 848, 1600, 975, 2754, 1804, 2484, 1348, 4908, 1533, 2744, 3764, 6660, 1820, 5191, 1916, 7423, 4617, 3882, 2347, 13130, 4129

Offset

1,1

Comments

There are finitely many imaginary biquadratic fields given a class number.

Links

Table of n, a(n) for n=1..25.

J. M. Basilla and I. A. C. Fajardo, Imaginary biquadratic number fields with small odd class numbers, Proc. Japan Acad. Ser. A Math. Sci. 102(1) (2026), 1-6.

D. A. Buell, H. C. Williams and K. S. Williams, On the imaginary bicyclic biquadratic fields with class-number 2, Math. Comp. 31(140) (1977), 1034-1042.

Example

There are a(1) = 160 imaginary biquadratic fields with class number 2.
There are a(2) = 408 imaginary biquadratic fields with class number 4.

Crossrefs

Cf. A159456, A378956.

Sequence in context: A367206 A127338 A138854 * A133530 A278129 A184070

Adjacent sequences: A390354 A390355 A390356 * A390358 A390359 A390360

Keyword

nonn,more

Author

Iana Angela C. Fajardo, Jan 27 2026

Status

approved