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

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A016031 De Bruijn's sequence: 2^(2^(n-1) - n): ways of arranging 2^n bits in circle so all 2^n consecutive strings of length n are distinct. 4
1, 1, 2, 16, 2048, 67108864, 144115188075855872, 1329227995784915872903807060280344576, 226156424291633194186662080095093570025917938800079226639565593765455331328 (list; graph; refs; listen; history; internal format)
OFFSET

1,3

COMMENTS

Sequence corresponds also to the largest number that may be determined by asking no more than 2^(n-1) - 1 questions("Yes"-or-"No" answerable)with lying allowed at most once. - Lekraj Beedassy (blekraj(AT)yahoo.com), Jul 15 2002

Number of Ouroborean rings for binary n-tuplets. - Lekraj Beedassy (blekraj(AT)yahoo.com), May 06 2004

Also the number of games of Nim that are wins for the second player when the starting position is either the empty heap or heaps of sizes 1 <= t_1 < t_2 < ... < t_k < 2^(n-1) (if n is 1, the only starting position is the empty heap). E.g.: a(4) = 16: the winning positions for the second player when all the heap sizes are different and less than 2^3: (4,5,6,7), (3,5,6), (3,4,7), (2,5,7), (2,4,6), (2,3,6,7), (2,3,4,5), (1,6,7), (1,4,5), (1,3,5,7), (1,3,4,6), (1,2,5,6), (1,2,4,7), (1,2,3), (1,2,3,4,5,6,7) and the empty heap. - Kennan Shelton (kennan.shelton(AT)gmail.com), Apr 14 2006

REFERENCES

J. L. Gross and J. Yellen, eds., Handbook of Graph Theory, CRC Press, 2004; p. 255.

F. Harary and E. Palmer, Graphical Enumeration, (1973), p. 31.

D. J. Newman, "A variation of the Game of Twenty Question", Prob. 66-20 pp. 121-2 In Problems in Applied Mathematics, Ed. M. S. Klamkin, SIAM PA 1990.

R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Cor. 5.6.15.

I. Stewart, Game, Set and Math, pp. 50, Penguin 1991.

LINKS

R. Erra, N. Lygeros and N. Stewart, On Minimal Strings Containing the Elements of S(n) by Decimation; Section 5.4

Wikipedia, De Bruijn sequence

FORMULA

a(n)=2^{A000295(n-1)}. - Lekraj Beedassy (blekraj(AT)yahoo.com), Jan 17 2007

MAPLE

P:=proc(n) local i, j; for i from 1 by 1 to n do j:=2^(2^(i-1)-i); print(j); od; end: P(20); - Paolo P. Lava (paoloplava(AT)gmail.com), May 11 2006

MATHEMATICA

Select[Table[Sqrt[2^n/n^2], {n, 2000}], IntegerQ] (* From Vladimir Joseph Stephan Orlovsky, Jan 21 2012 *)

CROSSREFS

Sequence in context: A102103 A060597 A091479 * A001309 A132569 A165644

Adjacent sequences:  A016028 A016029 A016030 * A016032 A016033 A016034

KEYWORD

nonn,easy,nice

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com), Robert G. Wilson v (rgwv(AT)rgwv.com)

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
Recent Additions | More pages | Superseeker | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified February 13 05:27 EST 2012. Contains 205435 sequences.