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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A227086 Number of n X 3 binary arrays indicating whether each 2 X 2 subblock of a larger binary array has lexicographically increasing rows and columns, for some larger (n+1) X 4 binary array with rows and columns of the latter in lexicographically nondecreasing order. 1
7, 29, 99, 302, 842, 2177, 5281, 12128, 26548, 55684, 112389, 219051, 413531, 758154, 1353017, 2355283, 4006629, 6671623, 10890535, 17450956, 27483624, 42589055, 65002969, 97810106, 145217866, 212903302, 308449369, 441889009, 626378657 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = (1/39916800)*n^11 + (1/3628800)*n^10 + (1/120960)*n^9 + (1/8640)*n^8 + (1481/1209600)*n^7 + (1153/172800)*n^6 + (14807/181440)*n^5 + (92843/362880)*n^4 + (10901/16800)*n^3 + (19709/7200)*n^2 + (20959/9240)*n + 1.

Conjectures from Colin Barker, Sep 07 2018: (Start)

G.f.: x*(7 - 55*x + 213*x^2 - 512*x^3 + 837*x^4 - 964*x^5 + 794*x^6 - 468*x^7 + 197*x^8 - 58*x^9 + 11*x^10 - x^11) / (1 - x)^12.

a(n) = 12*a(n-1) - 66*a(n-2) + 220*a(n-3) - 495*a(n-4) + 792*a(n-5) - 924*a(n-6) + 792*a(n-7) - 495*a(n-8) + 220*a(n-9) - 66*a(n-10) + 12*a(n-11) - a(n-12) for n>12.

(End)

EXAMPLE

Some solutions for n=4:

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

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

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

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

CROSSREFS

Column 3 of A227089.

Sequence in context: A042609 A002941 A193655 * A102485 A246038 A049349

Adjacent sequences:  A227083 A227084 A227085 * A227087 A227088 A227089

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jun 30 2013

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 November 13 20:57 EST 2019. Contains 329106 sequences. (Running on oeis4.)