login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A274988 Square spiral reflection. 0
1, 3, 5, 7, 9, 9, 9, 9, 11, 13, 13, 15, 17, 19, 21, 23, 25, 27, 27, 27, 27, 27, 27, 27, 29, 31, 33, 33, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 55, 57, 59, 61 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Draw a square spiral growing by a unit line segment on each step, and at the same time, draw another square spiral in the opposite direction (again using a unit line segment) that turns after the first step (see example). a(n) is the number of unit line segments remaining after the n-th step. Note that overlapping line segments are counted once.

LINKS

Table of n, a(n) for n=1..52.

EXAMPLE

                  __     ____      ____      ____     ____     ____

   __      __|    __|      __|    |  __|    |  __|   |  __|   |  __|

             |    __|    ____|    |____|    |____|   |____|   |____|

   n=1     n=2    n=3     n=4       n=5      n=6      n=7      n=8

--

                                                         __      __ __

________     ____ __      ____ __      ____ __|     ____ __|   ____ __|

|  __|      |  __|  |    |  __|  |    |  __|  |    |  __|  |  |  __|  |

|____|__    |____|__|    |____|__|    |____|__|    |____|__|  |____|__|

                                              |          __|     __ __|

   n=9        n=10         n=11         n=12          n=13       n=14

CROSSREFS

Sequence in context: A139081 A196189 A206543 * A265509 A265527 A217250

Adjacent sequences:  A274985 A274986 A274987 * A274989 A274990 A274991

KEYWORD

nonn

AUTHOR

Wesley Ivan Hurt, Dec 25 2016

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 19 18:29 EDT 2020. Contains 337181 sequences. (Running on oeis4.)