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.

Showing 1-3 of 3 results.

A385446 Decimal expansion of -7 + 10*phi, with the golden section phi = A001622.

Original entry on oeis.org

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

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Author

Wolfdieter Lang, Jul 01 2025

Keywords

Comments

This constant d gives the imaginary part of -2*11*Z = c + d*i, where Z is the fixed point of a complex function w (of the loxodromic type) mapping vertices of golden triangles, starting with vertices (D_1, D_2, D_3), circumcribed by the unit circle with center at the origin, and D_1 = i (the complex unit), D_2 = (s - phi*i)/2 and D_3 = (-s - phi*i)/2. This function is w(z) = a*z + b, with a = (-1 + phi) * exp(-3*Pi*i/5) = -((2 - phi) + s*i)/2 and b = (1 - phi)*i, where s = sqrt(3 - phi) = A182007 (the length of the base (D2, D3) of the first triangle).
The real part c = (-1 + 3*phi)*s is given in A385445.
For details see A385445, and eqs.(5a,b) of the linked paper there.

Examples

			9.18033988749894848204586834365638117720309179805762862...
		

Crossrefs

Programs

  • Mathematica
    RealDigits[10*GoldenRatio - 7, 10, 120][[1]] (* Amiram Eldar, Jul 02 2025 *)

Formula

Equals -7 + 10*phi, an integer in the quadratic number field Q(sqrt(5)).
Equals 10*A176055-12 = 10*A104457-17 = 10*A001622-7 . - R. J. Mathar, Jul 06 2025

A385447 Decimal expansion of sqrt(8 + 9*phi), with the golden section A001622.

Original entry on oeis.org

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

Views

Author

Wolfdieter Lang, Jul 01 2025

Keywords

Comments

This constant c gives sqrt(11)*rho_1, where rho_1 = length(Z, D_1), with the fixed point Z = -(A385445 + A385446*i)/(2*11) of the complex map w given in A385445 and D_1 = i.
See A385445 for details and the linked paper, eq. (7b).

Examples

			4.7499795682454312672720369270371548927...
		

Crossrefs

Programs

  • Mathematica
    RealDigits[Sqrt[8 + 9*GoldenRatio], 10, 120][[1]] (* Amiram Eldar, Jul 02 2025 *)

Formula

Equals sqrt(8 + 9*phi) = sqrt(5 + 7*phi)*s, with s = A182007, the length of the side of a regular pentagon circumcribed by a unit circle.

A385448 Decimal expansion of sqrt(5 + 7*phi)/sqrt(11), with the golden section phi = A001622.

Original entry on oeis.org

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

Views

Author

Wolfdieter Lang, Jul 01 2025

Keywords

Comments

This equals the ratio length(Z, D_1)/s, with the fixed point of a complex loxodromic map w mapping iteratively golden triangles, starting with the one inscribed in a circumcircle with center ot the origin of the complex plane, the top vertex D_1 = i (the complex unit) and the base D_2 = (s - phi*i)/2, D_3 = (-s - phi*i)/2, with s = A182007.
See A385445 for details and a linked paper.

Examples

			1.218278887359662291535460267917274745203687400531554...
		

Crossrefs

Programs

  • Mathematica
    RealDigits[Sqrt[(5 + 7*GoldenRatio)/11], 10, 120][[1]] (* Amiram Eldar, Jul 02 2025 *)

Formula

Equals sqrt(5 + 7*phi)/sqrt(11) = sqrt(5 + 7*phi)/A010468.
Showing 1-3 of 3 results.