login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Please make a donation (tax deductible in USA) to keep the OEIS running. Over 5000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A137466 1 concatenated with n 21's. 1
1, 121, 12121, 1212121, 121212121, 12121212121, 1212121212121, 121212121212121, 12121212121212121, 1212121212121212121, 121212121212121212121, 12121212121212121212121, 1212121212121212121212121, 121212121212121212121212121, 12121212121212121212121212121 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..100

Index entries for linear recurrences with constant coefficients, signature (101,-100).

FORMULA

From Colin Barker, May 31 2015: (Start)

  a(n) = (2^(3+2*n)*5^(1+2*n)-7)/33.

  a(n) = 100*a(n-1) + 21.

  a(n) = 101*a(n-1) - 100*a(n-2).

  G.f.: (20*x+1) / ((x-1)*(100*x-1)).

(End)

EXAMPLE

a(7) = 1 21 21 21 21 21 21 21.

MATHEMATICA

Table[FromDigits[PadRight[{1}, n, {1, 2}]], {n, 1, 31, 2}] (* or *) LinearRecurrence[{101, -100}, {1, 121}, 30] (* Harvey P. Dale, Aug 17 2013 *)

PROG

(PARI) Vec((20*x+1)/((x-1)*(100*x-1)) + O(x^30)) \\ Colin Barker, May 31 2015

CROSSREFS

Sequence in context: A054319 A006061 A079215 * A062689 A057139 A002477

Adjacent sequences:  A137463 A137464 A137465 * A137467 A137468 A137469

KEYWORD

easy,nonn,base

AUTHOR

Ctibor O. Zizka, Apr 19 2008

EXTENSIONS

More terms from Harvey P. Dale, Aug 17 2013

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified December 5 05:27 EST 2016. Contains 278761 sequences.