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
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Jun 08 2014
STATUS
approved