The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A208689 Number of 3 X n 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 1 1 and 1 0 1 vertically. 2
 6, 36, 78, 282, 768, 2430, 7086, 21588, 64230, 193554, 579264, 1740054, 5216502, 15655428, 46956702, 140885610, 422631744, 1267935822, 3803741790, 11411331636, 34233822966, 102701747106, 308104791168, 924315101862, 2772944127078 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Row 3 of A208688. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 2*a(n-1) + 4*a(n-2) - 3*a(n-3). Conjectures from Colin Barker, Mar 07 2018: (Start) G.f.: 6*x*(1 + 4*x - 3*x^2) / ((1 - 3*x)*(1 + x - x^2)). a(n) = 2^(-n)*(5*6^(2+n) + (75-27*sqrt(5))*(-1+sqrt(5))^n + 3*(-1-sqrt(5))^n*(25+9*sqrt(5))) / 55. (End) EXAMPLE Some solutions for n=4: ..0..1..0..0....1..1..0..1....0..1..1..0....1..1..0..0....0..1..0..0 ..1..1..1..0....1..1..1..1....0..1..1..0....0..1..0..1....1..1..1..1 ..0..1..0..1....0..1..0..0....1..0..1..1....0..1..1..0....0..1..0..0 CROSSREFS Cf. A208688. Sequence in context: A207730 A208103 A207724 * A207483 A207264 A207270 Adjacent sequences: A208686 A208687 A208688 * A208690 A208691 A208692 KEYWORD nonn AUTHOR R. H. Hardin, Mar 01 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified November 30 05:38 EST 2022. Contains 358431 sequences. (Running on oeis4.)