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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A047937 Number of 2-colorings of an n X n grid, up to rotational symmetry. 10
1, 2, 6, 140, 16456, 8390720, 17179934976, 140737496748032, 4611686019501162496, 604462909807864344215552, 316912650057057631849169289216, 664613997892457937028364283517337600 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Cycle index = 1/4(s_1^(n^2)+ 2 s_4^floor(n^2/4)s_1^(n mod 2)+s_2^floor(n^2/2)s_1^(n mod 2)). - Geoffrey Critzer, Oct 28 2011

LINKS

Table of n, a(n) for n=0..11.

FORMULA

a(n) = (m^(n^2) + 2*m^((n^2 + 3*(n mod 2))/4) + m^((n^2 + (n mod 2))/2))/4, with m = 2.

EXAMPLE

a(2)=6 from

00 10 11 10 11 11

00 00 00 01 10 11

MATHEMATICA

Table[(2^(n^2)+2*2^Floor[n^2/4]*2^Mod[n, 2]+2^Floor[n^2/2]*2^Mod[n, 2])/4, {n, 0, 10}]  (* Geoffrey Critzer, Oct 28 2011 *)

CROSSREFS

Cf. A054247, A047937-A047945.

Sequence in context: A206849 A090907 A159478 * A027731 A280821 A145143

Adjacent sequences:  A047934 A047935 A047936 * A047938 A047939 A047940

KEYWORD

nonn,easy,nice

AUTHOR

Rob Pratt

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 October 16 20:35 EDT 2019. Contains 328103 sequences. (Running on oeis4.)