cp's OEIS Frontend

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.

A309948 Decimal expansion of the real part of the square root of 1 + i.

Original entry on oeis.org

1, 0, 9, 8, 6, 8, 4, 1, 1, 3, 4, 6, 7, 8, 0, 9, 9, 6, 6, 0, 3, 9, 8, 0, 1, 1, 9, 5, 2, 4, 0, 6, 7, 8, 3, 7, 8, 5, 4, 4, 3, 9, 3, 1, 2, 0, 9, 2, 7, 1, 5, 7, 7, 4, 3, 7, 4, 4, 4, 1, 1, 5, 7, 8, 8, 4, 2, 8, 7, 5, 0, 5, 3, 5, 5, 5, 2, 8, 4, 8, 1, 1, 1, 3, 6, 5, 3, 6, 0, 6, 6, 3, 5, 6, 4, 1
Offset: 1

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Author

Alonso del Arte, Aug 24 2019

Keywords

Comments

i is the imaginary unit such that i^2 = -1.
Also imaginary part of sqrt(-1 + i).

Examples

			Re(sqrt(1 + i)) = 1.09868411346780996603980119524...
		

Crossrefs

Cf. A010060, A309949 (imaginary part).

Programs

  • Maple
    Digits := 120: Im(-sqrt(-1 - I))*10^95:
    ListTools:-Reverse(convert(floor(%), base, 10)); # Peter Luschny, Sep 20 2019
  • Mathematica
    RealDigits[Sqrt[1/2 + 1/Sqrt[2]], 10, 100][[1]]
  • PARI
    real(sqrt(1+I)) \\ Michel Marcus, Sep 16 2019

Formula

Re(sqrt(1 + i)) = sqrt(1/2 + 1/sqrt(2)) = 2^(1/4) * cos(Pi/8).
Equals Im(-sqrt(-1 - i)). - Peter Luschny, Sep 20 2019
Equals Product_{k>=0} ((8*k+3)*(8*k+5)/((8*k+1)*(8*k+7)))^A010060(k) (Allouche et al., 2019). - Amiram Eldar, Feb 04 2024