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!)
A243646 Number of ways three L-tiles can be placed on an n X n square. 2
0, 0, 0, 0, 11, 196, 1195, 4544, 13215, 32276, 69671, 137120, 251139, 434180, 715891, 1134496, 1738295, 2587284, 3754895, 5329856, 7418171, 10145220, 13657979, 18127360, 23750671, 30754196, 39395895, 49968224, 62801075, 78264836, 96773571, 118788320, 144820519 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..1000

FORMULA

G.f.: x^4*(x^5-27*x^4+90*x^3-54*x^2-119*x-11) / (x-1)^7.

a(n) = (n^6-6*n^5-6*n^4+88*n^3-73*n^2-310*n+426)/6 for n>=4, a(n) = 0 for n<4.

EXAMPLE

a(4) = 11:

._______.  ._______.  ._______.  ._______.

| |_|_|_|  | |_|_|_|  | |_| |_|  | |_| |_|

|___|_|_|  |___| |_|  |___|___|  |___|___|

| |_| |_|  | |_|___|  | |_|_|_|  |_| |_|_|

|___|___|  |___|_|_|  |___|_|_|  |_|___|_|

._______.  ._______.  ._______.  ._______.

| |_| |_|  |_|_| |_|  |_|_| |_|  |_| |_|_|

|___|___|  | |_|___|  |_|_|___|  |_|___|_|

|_|_| |_|  |___| |_|  | |_| |_|  | |_| |_|

|_|_|___|  |_|_|___|  |___|___|  |___|___|

._______.  ._______.  ._______.

|_|_| |_|  | |_|_|_|  |_| |_|_|

|_| |___|  |___| |_|  | |___|_|

| |___|_|  |_| |___|  |___| |_|

|___|_|_|  |_|___|_|  |_|_|___| .

MAPLE

a:= n-> `if`(n<4, 0, ((((((n-6)*n-6)*n+88)*n-73)*n-310)*n+426)/6):

seq(a(n), n=0..50);

CROSSREFS

Column k=3 of A243608.

Sequence in context: A201185 A345342 A218818 * A186251 A234628 A105124

Adjacent sequences:  A243643 A243644 A243645 * A243647 A243648 A243649

KEYWORD

nonn,easy

AUTHOR

Alois P. Heinz, Jun 08 2014

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 25 15:43 EDT 2022. Contains 356986 sequences. (Running on oeis4.)