A102264 Smallest prime for which 2^n exactly divides the class number h(-4p).

5, 17, 41, 257, 521, 4481, 9521, 21929, 72089, 531977, 1256009, 5014169, 20879129, 70993529, 258844361, 866941841, 3771185921

Offset

1,1

Links

Table of n, a(n) for n=1..17.

H. Cohn and J. C. Lagarias, On the existence of fields governing the 2-invariants of the classgroup of Q(sqrt{dp}) as p varies, Math. Comp. 41 (1983), 711-730.

S. Louboutin, L-functions and class numbers of imaginary quadratic fields and of quadratic extensions of an imaginary quadratic field, Math. Comp. 59 (1992) 213-230, Table 1

Prog

(Sage)
def a(n):
    for p in Primes():
        if QuadraticField(-p).class_number().valuation(2)==n:
            return p  # Robin Visser, May 25 2024

Crossrefs

Cf. A006641.

Sequence in context: A111268 A346706 A106973 * A122035 A052350 A318826

Adjacent sequences: A102261 A102262 A102263 * A102265 A102266 A102267

Keyword

nonn,more

Author

N. J. A. Sloane, Feb 19 2005

Extensions

a(10)-a(17) from Robin Visser, May 25 2024

Status

approved