The On-Line Encyclopedia of Integer Sequences® (OEIS®)

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A133288

Negative discriminants with form class group of exponent 2 (negated).
(history; published version)

#5 by Alois P. Heinz at Fri Jul 20 17:42:07 EDT 2018

STATUS

proposed

approved

#4 by Andrew Howroyd at Fri Jul 20 17:00:15 EDT 2018

STATUS

editing

proposed

#3 by Andrew Howroyd at Fri Jul 20 16:28:29 EDT 2018

LINKS

Andrew Howroyd, <a href="/A133288/b133288.txt">Table of n, a(n) for n = 1..88</a>

PROG

(PARI) ok(n)={(-n)%4<2 && quadclassunit(-n).no > 1 && !#select(k->k<>2, quadclassunit(-n).cyc)} \\ Andrew Howroyd, Jul 20 2018

STATUS

approved

editing

#2 by Russ Cox at Sat Mar 31 10:29:30 EDT 2012

AUTHOR

_David Brink (brink(AT)math.ku.dk), _, Dec 30 2007

Discussion
Sat Mar 31	10:29	OEIS Server: https://oeis.org/edit/global/606

#1 by N. J. A. Sloane at Sun Jun 29 03:00:00 EDT 2008

	NAME	`Negative discriminants with form class group of exponent 2 (negated).`
	DATA	`15, 20, 24, 32, 35, 36, 40, 48, 51, 52, 60, 64, 72, 75, 84, 88, 91, 96, 99, 100, 112, 115, 120, 123, 132, 147, 148, 160, 168, 180, 187, 192, 195, 228, 232, 235, 240, 267, 280, 288, 312, 315, 340, 352, 372, 403, 408, 420, 427, 435, 448, 480, 483, 520, 532, 555, 595, 627, 660, 672, 708, 715, 760`
	OFFSET	`1,1`
	REFERENCES	`D. A. Cox, Primes of the form x^2+ny^2, Wiley, New York, 1989.` `D. E. Flath, Introduction to Number Theory, Wiley-Interscience, 1989.`
	CROSSREFS	`Cf. A003171 is the disjoint union of A133675 and this sequence.`
	KEYWORD	`fini,nonn`
	AUTHOR	`David Brink (brink(AT)math.ku.dk), Dec 30 2007`
	STATUS	`approved`

Last modified August 30 20:27 EDT 2024. Contains 375546 sequences. (Running on oeis4.)