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

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A225976 Number of n X 2 binary arrays whose sum with another n X 2 binary array containing no more than two 1s has rows and columns in lexicographically nondecreasing order. 1

%I #8 Sep 05 2018 14:50:54

%S 4,15,48,138,350,790,1616,3049,5384,9001,14376,22092,32850,47480,

%T 66952,92387,125068,166451,218176,282078,360198,454794,568352,703597,

%U 863504,1051309,1270520,1524928,1818618,2155980,2541720,2980871,3478804,4041239

%N Number of n X 2 binary arrays whose sum with another n X 2 binary array containing no more than two 1s has rows and columns in lexicographically nondecreasing order.

%H R. H. Hardin, <a href="/A225976/b225976.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = (11/120)*n^5 - (1/8)*n^4 + (9/8)*n^3 - (7/8)*n^2 + (287/60)*n - 1.

%F Conjectures from _Colin Barker_, Sep 05 2018: (Start)

%F G.f.: x*(4 - 9*x + 18*x^2 - 5*x^3 + 2*x^4 + x^5) / (1 - x)^6.

%F a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>6.

%F (End)

%e Some solutions for n=3:

%e ..0..1....1..1....0..0....0..0....1..1....0..1....0..0....0..1....1..1....0..1

%e ..0..0....1..1....1..1....0..1....1..0....0..1....0..1....0..1....0..0....0..1

%e ..1..1....0..1....0..0....1..1....1..0....0..1....0..0....1..0....1..1....1..1

%Y Column 2 of A225982.

%K nonn

%O 1,1

%A _R. H. Hardin_, May 22 2013

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 29 04:23 EDT 2024. Contains 371264 sequences. (Running on oeis4.)