This site is supported by donations to The OEIS Foundation.

 Annual Appeal: Please make a donation to keep the OEIS running. In 2018 we replaced the server with a faster one, added 20000 new sequences, and reached 7000 citations (often saying "discovered thanks to the OEIS"). Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A041181 Denominators of continued fraction convergents to sqrt(101). 5
 1, 20, 401, 8040, 161201, 3232060, 64802401, 1299280080, 26050404001, 522307360100, 10472197606001, 209966259480120, 4209797387208401, 84405914003648140, 1692328077460171201, 33930967463207072160, 680311677341601614401 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Generalized Pell numbers (A000129). Antidiagonals of A038207. - Mark Dols, Aug 31 2009 a(n) equals the number of words of length n on alphabet {0,1,...,20} avoiding runs of zeros of odd lengths. - Milan Janjic, Jan 28 2015 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..200 Tanya Khovanova, Recursive Sequences Index entries for linear recurrences with constant coefficients, signature (20,1). FORMULA a(n) = F(n, 20), the n-th Fibonacci polynomial evaluated at x=20. - T. D. Noe, Jan 19 2006 a(n) = 20*a(n-1)+a(n-2) for n>1, a(0)=1, a(1)=20. G.f.: 1/(1-20*x-x^2). - Philippe Deléham, Nov 21 2008 a(n) = (5/101)*sqrt(101)*((10+sqrt(101))^n-(10-sqrt(101))^n)+(1/2)*((10 +sqrt(101))^n+(10-sqrt(101))^n). - Paolo P. Lava, Dec 03 2009 MATHEMATICA a=0; lst={}; s=0; Do[a=s-(a-1); AppendTo[lst, a]; s+=a*20, {n, 3*4!}]; lst (* Vladimir Joseph Stephan Orlovsky, Oct 27 2009 *) Denominator[Convergents[Sqrt[101], 30]] (* Vincenzo Librandi, Dec 12 2013 *) PROG (MAGMA) I:=[1, 20]; [n le 2 select I[n] else 20*Self(n-1)+Self(n-2): n in [1..30]]; // Vincenzo Librandi, Dec 12 2013 CROSSREFS Cf. A041180, A040090. Cf. similar sequences listed in A243399. Sequence in context: A007545 A055476 A223180 * A041762 A196740 A196898 Adjacent sequences:  A041178 A041179 A041180 * A041182 A041183 A041184 KEYWORD nonn,frac,easy,less AUTHOR STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 10 19:01 EST 2018. Contains 318049 sequences. (Running on oeis4.)