OFFSET
0,4
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
Wikipedia, Pentomino
FORMULA
G.f.: see Maple program.
EXAMPLE
a(4) = 3:
._______. ._______. ._______.
| | | | | | | ._. | | ._. | |
| | | | | | |_| |_| |_| |_| |
| | | | | | |_. ._| |_. ._| |
| | | | | | | |_| | | |_| | |
|_|_|_|_| |_|_____| |_____|_| .
MAPLE
gf:= -(x-1)^2 *(x^4+x^3+x^2+x+1)^2 /
(x^15 +x^13 +x^11 -3*x^10 -2*x^8 -2*x^6 +6*x^5 +x^3 +x-1):
a:= n-> coeff(series(gf, x, n+1), x, n):
seq(a(n), n=0..50);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Nov 19 2014
STATUS
approved