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.

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A197002 Decimal expansion of xo, where P=(xo,yo) is the point nearest O=(0,0) in which a line y=mx meets the curve y=cos(x+Pi/4) orthogonally.

Original entry on oeis.org

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

Views

Author

Clark Kimberling, Oct 09 2011

Keywords

Comments

See the Mathematica program for a graph.
xo=0.36954256660758032082765604383693...
yo=0.40397275329951720931896174006631...
m=1.093169744985016922088153214160579...
|OP|=0.547499492185436214325204150357...

Crossrefs

Programs

  • Maple
    evalf(solve(cos(x)=x,x)/2, 140);  # Alois P. Heinz, Feb 20 2024
  • Mathematica
    c = Pi/4;
    xo = x /. FindRoot[x == Sin[x + c] Cos[x + c], {x, .8, 1.2}, WorkingPrecision -> 100]
    RealDigits[xo] (* A197002 *)
    m = 1/Sin[xo + c]
    RealDigits[m]  (* A197003 *)
    yo = m*xo
    d = Sqrt[xo^2 + yo^2]
    Show[Plot[{Cos[x + c], yo - (1/m) (x - xo)}, {x, -Pi/4, 1}], ContourPlot[{y == m*x}, {x, 0, Pi}, {y, 0, 1}], PlotRange -> All, AspectRatio -> Automatic, AxesOrigin -> Automatic]
  • PARI
    solve(x=0,1,cos(x)-x)/2  \\ Gleb Koloskov, Jun 16 2021

Formula

Equals d/2 = A003957/2, where d is the Dottie number. - Gleb Koloskov, Jun 16 2021

A085984 Decimal expansion of solution to e^x*(-1 + x) = (1 + x)/e^x.

Original entry on oeis.org

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

Views

Author

Eric W. Weisstein, Jul 06 2003

Keywords

Comments

This constant can also be defined as the root of coth x = x, as this equation and the above are equivalent. - Carl R. White, Dec 09 2003. Also the root of x*tanh x = 1. - N. J. A. Sloane, May 07 2020
This constant is also the point on the parametric tractrix (t - tanh(t), sech(t)) the least distant from the origin. - Michael Clausen, Feb 18 2013
This constant also equals sqrt(lambda^2+1), where lambda is the Laplace limit constant A033259. - Jean-François Alcover, Sep 08 2014, after Steven Finch.
For each of the real symmetric n X n matrices M defined by M(i,j) = max(i,j) with n >= 2, there exist n-1 negative eigenvalues < -1/4 and only one positive eigenvalue lambda(n) such that n^2/2 < lambda(n) < n^2. Indeed, when n tends to infinity, lambda(n) ~ n^2/(this constant)^2 (see reference O. Carton et al.). For n = 2, the positive eigenvalue is (3+sqrt(17))/2 [A178255]. - Bernard Schott, Mar 13 2020

Examples

			1.1996786402577338339163698486411419442614587884186072...
		

References

  • O. Carton, L. Rosaz, M. Zeitoun, Problèmes corrigés de Mathématiques posés au Concours de Mines/Ponts, Tome 5, Ellipses, 1992; Problème Mines-Ponts 1991 - Options M, P', TA - Epreuve pratique p. 125.
  • Steven R. Finch, Mathematical constants, Volume 94, Encyclopedia of mathematics and its applications, Cambridge University Press, 2003, p. 268.
  • Jerome Spanier and Keith B. Oldham, "Atlas of Functions", Hemisphere Publishing Corp., 1987, chapter 30, equation 30:10:9 at page 283.

Crossrefs

Cf. A003957 (x = cos(x)), A009379, A033259, A069855, A209289.

Programs

  • Mathematica
    RealDigits[ x /. FindRoot[ Coth[x] == x, {x, 1}, WorkingPrecision -> 102]] // First (* Jean-François Alcover, Feb 08 2013 *)
    1+2 NSum[LaguerreL[n-1,1,4 n]/n Exp[-2 n],{n,1,Infinity}] //
      (* Aaron Hendrickson, Mar 17 2021 *)
  • PARI
    solve(u=1,2,tanh(u)-1/u)  /* type e.g. \p99 to get 99 digits; M. F. Hasler, Feb 01 2011 */

Formula

Equals 1 + 2*Sum_{n>=1} (Laguerre(n-1,1,4n)/n)*e^(-2n) (see Mathematics Stack Exchange in Links). - Aaron Hendrickson, Mar 17 2022

A332500 Decimal expansion of the maximal normal distance between sine and cosine; see Comments.

Original entry on oeis.org

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

Views

Author

Clark Kimberling, May 05 2020

Keywords

Comments

Let S and C denote the graphs of y = sin x and y = cos x. For each point (u, sin u) on S, let S(u) be the line normal to S at (u, sin u), and let (snc u, cos(snc u)) be the point of intersection of S(u) and C. Let d(u) be the distance from (u,sin u) to (snc u, cos(snc u)). We call d(u) the u-normal distance from S to C and note that in [0,Pi], there is a unique number u' such that d(u') > d(u) for all real numbers u except those of the form u' + k*Pi. We call d(u') the maximal normal distance between sine and cosine, and we call snc the sine-normal-to-cosine function.
For each (v, cos v) on C, let C(u) be the line normal to C at (v, cos v), and let (cns v, sin(cns v)) be the point of intersection of C(u) and S. Let e(v) be the distance from (v, cos v) to (cns v, sin(cns v)). We call d(v) the v-normal distance from C to S and note that there exists a unique number v' that maximizes e, and e(v') = d(u'). We call cns the cosine-normal-to-sine function. The numbers u' and v' are given in A332501 and A332503.
Note that the maximal normal distance (see Example) exceeds the normal distance from (Pi/2,1) in sine to (Pi/2,0) in cosine - possibly a surprise!

Examples

			2.72573705679992524967463858129656... = the number u in [0,2 Pi] such that the line normal to S at (u, sin u) passes through the point (3 Pi/4,0); cf. A332501.
0.4039727532995172093189617400663... = sin u; cf. A086751.
1.0949989843708724286504083007155... = maximal normal distance between sine and cosine.
1.9866519235847646080193264936226... = snc u; cf A332503.
		

Crossrefs

Programs

  • Mathematica
    Plot[{Sin[x], Cos[x]}, {x, -Pi, 3 Pi}, AspectRatio -> Automatic,
    ImageSize -> 600, PlotLabel -> "sine and cosine"]
    t = Table[x = x /. FindRoot[Cos[x] == -x Sec[u] + u Sec[u] + Sin[u], {x, 0}], {u, -2 Pi, 2 Pi, Pi/101}];
    ListPlot[t, PlotLabel -> "y \[Equal] snc(x)"]
    ListPlot[Cos[t], PlotLabel -> "y \[Equal] cos(snc(x))"]
    t = Table[x = x /. FindRoot[Sin[x] == x Csc[u] - u Csc[u] + Cos[u], {x, 0.1}], {u, -2 Pi + .01, 2 Pi - .01, Pi/101}];
    ListPlot[t, PlotLabel -> "y \[Equal] cns(x)"]
    ListPlot[Sin[t], PlotLabel -> "y \[Equal] sin(cns(x))"]
    u = u /. FindRoot[0 == (-3 Pi/4) Sec[u] + u Sec[u] + Sin[u], {u, 1}, WorkingPrecision ->120]  (* A332501 *)
    y = Sin[u]  (* A086751 *)
    d = 2*Sqrt[(u - 3 Pi/4)^2 + y^2]  (* A332500 *)
    RealDigits[u][[1]]  (* A332501 *)
    RealDigits[y][[1]]  (* A086751 *)
    RealDigits[d][[1]]  (* A332500 *)
  • PARI
    my(d=solve(x=0,1,cos(x)-x)); sqrt(d^2+2-2*sqrt(1-d^2)) \\ Gleb Koloskov, Jun 16 2021

Formula

d(u') = 2*sqrt((u - 3 Pi/4)^2 + (sin u)^2).
Equals sqrt(d^2+2-2*sqrt(1-d^2)) where d = A003957. - Gleb Koloskov, Jun 16 2021

A177413 Continued fraction expansion of the constant x defined by x = cos(x).

Original entry on oeis.org

0, 1, 2, 1, 4, 1, 40, 1, 9, 4, 2, 1, 15, 2, 12, 1, 21, 1, 17, 52, 3, 1, 6, 1, 2, 2, 1, 1, 2, 82, 1, 1, 2, 39, 27, 1, 15, 1, 1, 1, 2, 26, 1, 10, 1, 2, 1, 1, 1, 6, 1, 4, 1, 4839, 1, 2, 1, 4, 7, 2, 1, 43, 1, 21, 1, 5, 2, 1, 6, 4, 9, 2, 19, 1, 1, 2, 1, 1, 2, 38
Offset: 0

Views

Author

Ben Branman, Dec 10 2010

Keywords

Crossrefs

Cf. A003957.

Programs

  • Mathematica
    FindRoot[x == Cos[x], {x, 0}, WorkingPrecision -> 10000]; z = x /. %; ContinuedFraction[z]

A086751 Decimal expansion of the solution to x*sqrt(1-x^2) + arcsin(x) = Pi/4, or the length of the line connecting the origin to the center of the chord of a circle, centered at 0 and of radius 1, that divides the circle such that 1/4 of the area is on one side and 3/4 is on the other side.

Original entry on oeis.org

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

Views

Author

Jonathan R. Anderson (neo__jon(AT)hotmail.com), Jul 30 2003

Keywords

Comments

Decimal expansion of the number sin(u'), where u' is the number in [0,2 Pi] such that the line normal to the graph of y = sin x at (u', sin u') passes through the point (3 Pi/4,0). See A332500. - Clark Kimberling, May 05 2020

Examples

			0.403972753299517...
		

Crossrefs

Cf. A003957.

Programs

  • Maple
    Digits := 240 ; x := 0.4 ; for i from 1 to 8 do f := sin(2.0*x)+2.0*x-Pi/2.0 ; fp := 2*cos(2*x)+2.0 ; x := x-evalf(f/fp) ; printf("%.120f\n",sin(x)) ; od: x := sin(x) ; read("transforms3") ; CONSTTOLIST(x) ; # R. J. Mathar, May 19 2009
  • Mathematica
    digits = 105; Sin[FindRoot[Sin[2*a]/2+a == Pi/4, {a, 1/2}, WorkingPrecision -> digits][[1, 2]]] // RealDigits[#, 10, digits]& // First (* Jean-François Alcover, Feb 21 2014 *)
  • PARI
    solve(x=0, 1, x*sqrt(1-x^2) + asin(x) - Pi/4) \\ Michel Marcus, May 05 2020
    
  • PARI
    my(d=solve(x=0,1,cos(x)-x)); sqrt(2-2*sqrt(1-d^2))/2 \\ Gleb Koloskov, Jun 16 2021

Formula

Define k(n+1) as k(n) - (k(n)*sqrt(1-k(n)^2) + arcsin(k(n)) - Pi/4). The sequence is the decimal expansion of lim_{n -> infinity} k(n).
Equals sqrt(2-2*sqrt(1-d^2))/2, where d = A003957 is the Dottie number. - Gleb Koloskov, Jun 16 2021

Extensions

More terms from Jim Nastos, Sep 05 2003
More digits from R. J. Mathar, May 19 2009

A124597 Decimal expansion of the solution to x^2 = sin(x).

Original entry on oeis.org

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

Views

Author

Denton J. Dailey (djd1497(AT)aol.com), Dec 18 2006

Keywords

Comments

Fixed point of cardinal sine (sinc) function. - Michal Paulovic, Jun 13 2023

Examples

			0.87672621539506244597211864314192813997168545140130499558964277342...
		

Crossrefs

Cf. A003957.

Programs

  • Maple
    Digits:=105;fsolve(sin(x)/x-x,x); # Michal Paulovic, Jun 13 2023
  • Mathematica
    RealDigits[ FindRoot[ Sin[x] == x^2, {x, {.7, 1}}, WorkingPrecision -> 120][[1, 2, 1]], 10, 111][[1]]
  • PARI
    solve(x=0.8,0.9,sin(x)/x-x) \\ Michal Paulovic, Jun 13 2023

Extensions

More terms from Robert G. Wilson v, Dec 21 2006

A200309 Expansion of e.g.f.: 1/(cos(x) - x).

Original entry on oeis.org

1, 1, 3, 12, 65, 440, 3571, 33824, 366113, 4458240, 60321091, 897774592, 14576528801, 256391130112, 4856647308787, 98567413125120, 2133825372539585, 49080991762153472, 1195339768057071619, 30729146849826701312, 831545527540481198465, 23627123985544955559936
Offset: 0

Views

Author

Paul D. Hanna, Nov 15 2011

Keywords

Comments

Radius of convergence |x| < r, where r = cos(r) = 0.739085133215160... (A003957).
The continued fraction converges in the whole complex plane, cut along |z|=infinity.

Examples

			E.g.f.: A(x) = 1 + x + 3*x^2/2! + 12*x^3/3! + 65*x^4/4! + 440*x^5/5! +...
where 1/A(x) = 1 - x - x^2/2! + x^4/4! - x^6/6! +...
Special values.
A(Pi/5) = 10/(5*(sqrt(5)+1)/2 - 2*Pi) = 5.534081362740...
A(Pi/6) = 6/(3*sqrt(3) - Pi) = 2.920333635550...
A(Pi/8) = 8/(4*sqrt(2+sqrt(2)) - Pi) = 1.882599403781...
A(Pi/10) = 10/(5*sqrt(10+sqrt(20))/2 - Pi) = 1.5701119741529...
A(Pi/12) = 12/(6*sqrt(2+sqrt(3)) - Pi) = 1.4201994774470...
		

Crossrefs

Programs

  • Magma
    m:=30; R:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!(1/(Cos(x) - x))); [Factorial(n-1)*b[n]: n in [1..m]]; // G. C. Greubel, Jul 10 2018
  • Mathematica
    CoefficientList[Series[1/(Cos[x]-x), {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, Jun 27 2013 *)
  • PARI
    {a(n)=n!*polcoeff(1/(cos(x+x*O(x^n))-x),n)}
    
  • PARI
    x='x+O('x^30); Vec(serlaplace(1/(cos(x) - x))) \\ G. C. Greubel, Jul 10 2018
    

Formula

E.g.f.: E(x)=1/(cos(x) - x) = (1-x^2/((x-1)*G(0) + x^3))/(1-x); G(k)= 2*(2*k+1)*(k+1) - x^2 + 2*x^2*(2*k+1)*(k+1)/G(k+1); (continued fraction Euler's kind, 1-step). - Sergei N. Gladkovskii, Jan 08 2012
E.g.f.: 1/(G(0) - x) where G(k) = 1 - x^2/((4*k+1)*(4*k+2) - x^2*(4*k+1)*(4*k+2)/(x^2 - 4*(k+1)*(4*k+3)/G(k+1) )); - Sergei N. Gladkovskii, Dec 16 2012
a(n) ~ n!/((sin(r)+1)*r^(n+1)), where r = 0.73908513321516... is the root of the equation r = cos(r). - Vaclav Kotesovec, Jun 27 2013

A302977 Numerators of the rational factor of Kaplan's series for the Dottie number.

Original entry on oeis.org

1, -1, -1, -43, -223, -60623, -764783, -107351407, -2499928867, -596767688063, -22200786516383, -64470807442488761, -3504534741776035061, -3597207408242668198973, -268918457620309807441853, -185388032403184965693274807, -18241991360742724891839902347
Offset: 0

Views

Author

Ozaner Hansha, Apr 16 2018

Keywords

Comments

In Kaplan's original article, where the term "Dottie" was coined, he mentioned that while the number was indeed transcendental, it was possible to express it as an infinite sum with the general term r_n*Pi^(2n+1) where r_n was a sequence of rational numbers.

Examples

			The partial Kaplan series at n=3 is d = Pi/4 - Pi^3/768 - Pi^5/61440 - 43*Pi^7/165150720.
		

Crossrefs

Cf. A306254 (denominators).

Programs

  • Mathematica
    f[x_] := x - Cos[x]; g[x_] := InverseFunction[f][x]; s = {1}; Do[AppendTo[s, Numerator[(-1/2)^n * 1/n! * Derivative[n][g][Pi/2]]], {n, 3, 30, 2}]; s (* Amiram Eldar, Jan 31 2019 *)

Formula

These are the numerators of the unique sequence of rational numbers r_n such that d = Sum_{n>=0} r_n*Pi^(2*n+1) (where d is the Dottie number A003957).
r_0 = 1/4 and for n>0, r_n = b_(2*n+1); where b_n = g^(n)(Pi/2)/(2^n*n!) (and g^(n) is the n-th derivative of the inverse of x - cos(x)). A proof of this can be found in the second Hansha link.

Extensions

More terms from Amiram Eldar, Jan 31 2019

A306254 Denominators of the rational factor of Kaplan's series for the Dottie number.

Original entry on oeis.org

4, 768, 61440, 165150720, 47563407360, 669692775628800, 417888291992371200, 2808209322188734464000, 3055331742541343096832000, 33437550590372458851729408000, 56175084991825730870905405440000, 7276695809501137874093602599075840000, 17464069942802730897824646237782016000000
Offset: 0

Views

Author

Amiram Eldar, Feb 01 2019

Keywords

Comments

These are the denominators of the unique sequence of rational numbers r_n such that d = Sum_{n>=0} r_n*Pi^(2*n+1) (where d is the Dottie number A003957). The numerators are in A302977.

Examples

			The Kaplan series begins with d = Pi/4 - Pi^3/768 - Pi^5/61440 - 43*Pi^7/165150720 - ...
		

Crossrefs

Programs

  • Mathematica
    f[x_] := x - Cos[x]; g[x_] := InverseFunction[f][x]; s = {}; Do[AppendTo[s, Denominator[(-1/2)^n * 1/n! * Derivative[n][g][Pi/2]]], {n, 1, 30, 2}]; s

A125578 Decimal expansion of positive root of x^2 = cos(x).

Original entry on oeis.org

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

Views

Author

Denton J. Dailey (djd1497(AT)aol.com), Jan 03 2007

Keywords

Comments

Both roots have same magnitude: x = +-0.824132312302...
Fixed point of cos(x)/x function. - Michal Paulovic, Jun 13 2023

Examples

			0.824132312302522422960956785771991108142689866748289991732...
		

Crossrefs

Programs

  • Maple
    Digits:=100;fsolve(cos(x)/x-x,x); # Michal Paulovic, Jun 13 2023
  • Mathematica
    RealDigits[FindRoot[Cos[x] == x^2, {x, {.7, 1}}, WorkingPrecision -> 120][[1, 2, 1]], 10, 111][[1]]
  • PARI
    solve(x=0,1,cos(x)-x^2) \\ Charles R Greathouse IV, Apr 14 2014
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