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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A040420 Continued fraction for sqrt(442).

Original entry on oeis.org

21, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42
Offset: 0

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Keywords

Examples

			21 + 1/(42 + 1/(42 + 1/(42 + 1/(42 + ...)))) = sqrt(442).
		

Crossrefs

Cf. A041840/A041841 (convergents).

Programs

  • Maple
    with(numtheory): Digits := 300: convert(evalf(sqrt(442)),confrac);
  • Mathematica
    Block[{$MaxExtraPrecision=1000}, ContinuedFraction[Sqrt[442],120]] (* or *) PadRight[{21},120,{42}] (* Harvey P. Dale, Nov 28 2024 *)

Formula

From Elmo R. Oliveira, Feb 15 2024: (Start)
a(n) = 42 for n >= 1.
G.f.: 21*(1+x)/(1-x).
E.g.f.: 42*exp(x) - 21.
a(n) = 21*A040000(n) = 7*A040006(n) = 3*A040042(n). (End)

A041840 Numerators of continued fraction convergents to sqrt(442).

Original entry on oeis.org

21, 883, 37107, 1559377, 65530941, 2753858899, 115727604699, 4863313256257, 204374884367493, 8588608456690963, 360925930065387939, 15167477671202984401, 637394988120590732781, 26785756978736013761203
Offset: 0

Views

Author

Keywords

Crossrefs

Cf. A041841.

Programs

  • Mathematica
    Numerator[Convergents[Sqrt[442], 30]] (* or *) LinearRecurrence[{42, 1}, {21, 883}, 30] (* Harvey P. Dale, Nov 20 2012 *)
    CoefficientList[Series[(21 + x)/(1 - 42 x - x^2), {x, 0, 25}], x] (* Vincenzo Librandi, Nov 10 2013 *)

Formula

G.f.: (21+x)/(1-42*x-x^2). [Philippe Deléham, Nov 23 2008]
a(n) = 42*a(n-1)+a(n-2) for n>1, a(0)=21, a(1)=883. [Philippe Deléham, Nov 23 2008]
Showing 1-2 of 2 results.