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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A213120 Number of binary arrays of length 2*n+2 with fewer than n ones in any length 2n subsequence (=less than 50% duty cycle). 1
1, 10, 54, 252, 1110, 4748, 19964, 83024, 342678, 1406748, 5751636, 23443240, 95319484, 386805112, 1567130168, 6340730552, 25626393878, 103472018492, 417449893988, 1682982404072, 6780908053268, 27306234108392, 109907864408648 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row 3 of A213118.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Recurrence: n*(5*n-13)*a(n) = 2*(20*n^2-67*n+40)*a(n-1) - 8*(2*n-5)*(5*n-8) * a(n-2). - Vaclav Kotesovec, Oct 19 2012

a(n) = 2^(2*n+1) - (15*n-8)*C(2*n-2,n-1)/n. - Vaclav Kotesovec, Oct 29 2012

EXAMPLE

Some solutions for n=3

..0....0....0....0....1....1....0....0....0....0....0....0....0....1....0....1

..0....1....0....0....0....0....0....1....0....0....0....0....1....1....0....0

..0....1....1....0....1....1....0....0....0....0....0....1....0....0....1....0

..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0

..0....0....0....0....0....0....1....1....0....0....0....1....0....0....0....1

..1....0....1....0....0....0....0....0....0....1....0....0....0....0....0....0

..0....0....0....0....0....0....0....0....1....1....0....0....1....0....0....1

..0....1....0....0....0....1....1....0....0....0....1....0....1....1....1....0

MATHEMATICA

Table[2^(2*n+1)-(15*n-8)*Binomial[2*n-2, n-1]/n, {n, 1, 20}] (* Vaclav Kotesovec, Oct 29 2012 *)

CROSSREFS

Sequence in context: A058645 A170940 A057586 * A198770 A222539 A219623

Adjacent sequences:  A213117 A213118 A213119 * A213121 A213122 A213123

KEYWORD

nonn

AUTHOR

R. H. Hardin Jun 05 2012

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 17 06:08 EDT 2019. Contains 328106 sequences. (Running on oeis4.)