A167169 a(n) is the number of isomorphism classes of iterated quadratic extensions of the field of rationals of degree 2^n that ramify only at 2.

1, 3, 7, 36, 1131

Offset

0,2

Links

Table of n, a(n) for n=0..4.

Example

 a(1)=3 since Q[X]/(X^2-z) ramifies only at 2 iff z= -1, 2, -2 (up to squares).

Crossrefs

Sequence in context: A081010 A100377 A270396 * A269995 A281093 A199347

Adjacent sequences: A167166 A167167 A167168 * A167170 A167171 A167172

Keyword

nonn

Author

Gaël Collinet, Oct 29 2009

Status

approved