OFFSET
0,5
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
FORMULA
G.f.: -(x-1) *(x+1) *(x^3+x-1) *(x^3+x+1) *(x^11 -x^10 +x^9 -x^8 +x^7 -2*x^6 -x^5 +x^4 -x^3 +x^2 -x+1) / (x^27 -x^26 +5*x^25 -5*x^24 +9*x^23 -8*x^22 +3*x^21 -5*x^20 -18*x^19 +12*x^18 -29*x^17 +29*x^16 -17*x^15 +32*x^14 +16*x^13 -13*x^12 +25*x^11 -28*x^10 +15*x^9 -18*x^8 -4*x^7 +5*x^6 -5*x^5 +5*x^4 -2*x^3 +2*x^2 +x-1).
EXAMPLE
a(4) = 5:
._._._._. ._._._._. ._._._._. ._._._._. ._._._._.
| | | | | | | | | | | | |
| | |___|___| |___|___| | | |___|___|
| | | | | | | | | | | |
|_______| |___|___| | | |_______| |___|___|
| | | | | | | | | | | |
| | | | |_______| |___|___| |___|___|
| | | | | | | | | | | | |
|_______| |_______| |___|___| |___|___| |___|___|
MAPLE
a:= n-> coeff(series(-(x-1) *(x+1) *(x^3+x-1) *(x^3+x+1) *(x^11 -x^10 +x^9 -x^8 +x^7 -2*x^6 -x^5 +x^4 -x^3 +x^2 -x+1) / (x^27 -x^26 +5*x^25 -5*x^24 +9*x^23 -8*x^22 +3*x^21 -5*x^20 -18*x^19 +12*x^18 -29*x^17 +29*x^16 -17*x^15 +32*x^14 +16*x^13 -13*x^12 +25*x^11 -28*x^10 +15*x^9 -18*x^8 -4*x^7 +5*x^6 -5*x^5 +5*x^4 -2*x^3 +2*x^2 +x-1), x, n+1), x, n):
seq(a(n), n=0..60);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Jun 05 2013
STATUS
approved