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A003171 Negated discriminants of orders of imaginary quadratic fields with 1 class per genus (a finite sequence).
(Formerly M2331 N0922)
5
3, 4, 7, 8, 11, 12, 15, 16, 19, 20, 24, 27, 28, 32, 35, 36, 40, 43, 48, 51, 52, 60, 64, 67, 72, 75, 84, 88, 91, 96, 99, 100, 112, 115, 120, 123, 132, 147, 148, 160, 163, 168, 180, 187, 192, 195, 228, 232, 235, 240, 267, 280, 288, 312, 315, 340, 352, 372, 403 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

It is conjectured that a(101) = 7392 is the last term. If it would exist, a(102) > 10^6. - Hugo Pfoertner, Dec 01 2019

REFERENCES

Z. I. Borevich and I. R. Shafarevich, Number Theory. Academic Press, NY, 1966, pp. 425-430.

L. E. Dickson, Introduction to the Theory of Numbers. Dover, NY, 1957, p. 85.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..101

Rick L. Shepherd, Binary quadratic forms and genus theory, Master of Arts Thesis, University of North Carolina at Greensboro, 2013.

Jianing Song, List of the corresponding class groups

PROG

(PARI) ok(n)={(-n)%4<2 && !#select(k->k<>2, quadclassunit(-n).cyc)} \\ Andrew Howroyd, Jul 20 2018

CROSSREFS

Cf. A000926, A133288.

The fundamental terms are given in A003644.

Sequence in context: A154708 A227148 A026444 * A028970 A309388 A188259

Adjacent sequences:  A003168 A003169 A003170 * A003172 A003173 A003174

KEYWORD

nonn,fini

AUTHOR

N. J. A. Sloane, Mira Bernstein

EXTENSIONS

Terms a(44) and beyond from Andrew Howroyd, Jul 20 2018

STATUS

approved

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Last modified July 12 23:28 EDT 2020. Contains 335669 sequences. (Running on oeis4.)