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)

A041841 Denominators of continued fraction convergents to sqrt(442).

Original entry on oeis.org

1, 42, 1765, 74172, 3116989, 130987710, 5504600809, 231324221688, 9721121911705, 408518444513298, 17167495791470221, 721443341686262580, 30317787846614498581, 1274068532899495202982, 53541196169625413023825, 2250004307657166842203632
Offset: 0

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Author

Keywords

Comments

From Michael A. Allen, Aug 08 2023: (Start)
Also called the 42-metallonacci sequence; the g.f. 1/(1-k*x-x^2) gives the k-metallonacci sequence.
a(n) is the number of tilings of an n-board (a board with dimensions n X 1) using unit squares and dominoes (with dimensions 2 X 1) if there are 42 kinds of squares available. (End)

Crossrefs

Row n=42 of A073133, A172236 and A352361 and column k=42 of A157103.

Programs

Formula

a(n) = F(n, 42), the n-th Fibonacci polynomial evaluated at x=42. - T. D. Noe, Jan 19 2006
From Philippe Deléham, Nov 23 2008: (Start)
a(n) = 42*a(n-1) + a(n-2) for n > 1; a(0)=1, a(1)=42.
G.f.: 1/(1 - 42*x - x^2).
(End)

Extensions

Additional term from Colin Barker, Nov 25 2013
Showing 1-2 of 2 results.