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
KEYWORD
nonn,fini
AUTHOR
EXTENSIONS
Terms a(44) and beyond from Andrew Howroyd, Jul 20 2018
STATUS
approved