login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A106753 Discriminants, negated, of definite binary quadratic forms. 0
3, 7, 8, 11, 12, 15, 19, 20, 23, 24, 27, 28, 31, 32, 35, 39, 40, 43, 44, 47, 48, 51, 52, 55, 56, 59, 60, 63, 67, 68, 71, 72, 75, 76, 79, 80, 83, 84, 87, 88, 91, 92, 95, 96, 99, 103, 104, 107, 108, 111, 112, 115, 116, 119, 120, 123, 124, 127, 128, 131, 132, 135, 136, 139 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A definite binary quadratic form a*x^2 + b*x*y + c*y^2 over the integers has discriminant D = b^2 - 4*a*c < 0; -D is assumed to be a nonsquare.

LINKS

Table of n, a(n) for n=1..64.

FORMULA

-a(n) is 0 (mod 4) or 1 (mod 4), but not a square.

MATHEMATICA

Select[ Range[148], (Mod[ -#, 4] == 0 || Mod[ -#, 4] == 1) && !IntegerQ[Sqrt[ # ]] & ]

CROSSREFS

Cf. A014601, A042948 (with squares), A079896 (indefinite case).

Sequence in context: A283759 A261415 A285164 * A174871 A062863 A194470

Adjacent sequences:  A106750 A106751 A106752 * A106754 A106755 A106756

KEYWORD

easy,nonn

AUTHOR

Steven Finch, May 16 2005

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 17 15:32 EST 2020. Contains 331998 sequences. (Running on oeis4.)