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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A106753 Discriminants, negated, of definite binary quadratic forms.

Original entry on oeis.org

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
Offset: 1

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Author

Steven Finch, May 16 2005

Keywords

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.

Crossrefs

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

Programs

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

Formula

-a(n) is 0 (mod 4) or 1 (mod 4), but not a square.
Previous Showing 41-41 of 41 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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