login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A222940 Number of n X 2 0..4 arrays with no element equal to another at a city block distance of exactly two, and new values 0..4 introduced in row major order. 1
2, 7, 33, 273, 2433, 21873, 196833, 1771473, 15943233, 143489073, 1291401633, 11622614673, 104603532033, 941431788273, 8472886094433, 76255974849873, 686303773648833, 6176733962839473, 55590605665555233, 500315450989997073 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 2 of A222944.

LINKS

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

FORMULA

Empirical: a(n) = 10*a(n-1) - 9*a(n-2) for n>4.

Conjectures from Colin Barker, Aug 16 2018: (Start)

G.f.: x*(2 - 13*x - 19*x^2 + 6*x^3) / ((1 - x)*(1 - 9*x)).

a(n) = 3 + 10*3^(2*n-5) for n>2

(End)

EXAMPLE

Some solutions for n=3:

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

..2..3....2..3....2..3....1..1....2..2....2..3....1..1....1..2....2..3....0..1

..1..4....4..0....4..4....2..2....1..0....2..0....2..3....3..3....1..0....2..3

CROSSREFS

Cf. A222944.

Sequence in context: A232690 A143889 A241767 * A227120 A023053 A058915

Adjacent sequences:  A222937 A222938 A222939 * A222941 A222942 A222943

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 09 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 January 21 06:14 EST 2021. Contains 340333 sequences. (Running on oeis4.)