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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A011946 Number of Barlow packings with group P63/mmc(S) that repeat after 4n layers. 1
1, 2, 3, 8, 15, 30, 63, 128, 252, 510, 1023, 2040 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..12.

T. J. McLarnan, The numbers of polytypes in close packings and related structures, Zeits. Krist. 155, 269-291 (1981).

FORMULA

Conjecture: a(n) = n*floor(2^n/(2*n)). - Zerinvary Lajos, Apr 02 2007

CROSSREFS

Cf. A195095.

Sequence in context: A099428 A099920 A128022 * A195095 A166920 A242510

Adjacent sequences:  A011943 A011944 A011945 * A011947 A011948 A011949

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

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 17 19:16 EDT 2019. Contains 327137 sequences. (Running on oeis4.)