OFFSET
0,5
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
FORMULA
G.f.: 2*x^4*(465*x^11 -2767*x^10 -1161*x^9 -3873*x^8 +262965*x^7 -1067787*x^6 +1243269*x^5 +2069157*x^4 -9734826*x^3 -7263594*x^2 -967832*x -16896) / (x-1)^11.
a(n) = (5464830 -2069823*n -2896628*n^2 +1279635*n^3 +493090*n^4 -285192*n^5 -22560*n^6 +27360*n^7 -1600*n^8 -960*n^9 +128*n^10)/15 for n>=5, a(4) = 33792, a(n) = 0 for n<=3.
EXAMPLE
a(4) = 33792:
+-------+ +-------+
|o-o o | | o o|
| \ | | / ||
| o o| |o o o o|
| \ | | X |
|o o o| | o o |
|| / | | |
|o o | | o-o |
+-------+ +-------+ ... .
MAPLE
a:= n-> `if`(n<5, [0$4, 33792][n+1], ((((((((((128*n-960)*n-1600)*n
+27360)*n-22560)*n-285192)*n+493090)*n+1279635)*n-2896628)
*n-2069823)*n+5464830)/15):
seq(a(n), n=0..30);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Jun 05 2014
STATUS
approved