OFFSET
1,2
LINKS
J.-J. Bode, H. Harborth and M. Harborth, King independence on triangle boards, Discr. Math., 266 (2003), 101-107.
Index entries for linear recurrences with constant coefficients, signature (1,0,1,-1,0,1,-1,0,-1,1).
FORMULA
a(n)= a(n-1) +a(n-3) -a(n-4) +a(n-6) -a(n-7) -a(n-9) +a(n-10), n>12.
G.f.: x*(x^11 -x^10 -x^8 -x^7 -3*x^6 -2*x^5 -3*x^4 -3*x^3 -2*x^2 -2*x -1) / ((x -1)^3*(x +1)*(x^2 -x +1)*(x^2 +x +1)^2). - Colin Barker, Aug 06 2014
MAPLE
A082874 := proc(n)
if n = 1 then
1;
elif n = 2 then
3;
else
m := modp(n, 6) ;
3*n^2+op(m+1, [0, n+2, 2*n-4, 3, n+2, 2*n-1]) ;
%/6 ;
end if ;
end proc:
seq(A082874(n), n=1..50) ; # R. J. Mathar, Aug 05 2014
PROG
(Magma) I:=[1, 3, 5, 9, 14, 18, 26, 34, 41, 52, 64, 72]; [n le 12 select I[n] else Self(n-1)+Self(n-3)-Self(n-4)+Self(n-6)-Self(n-7)-Self(n-9)+Self(n-10): n in [1..60]]; // Vincenzo Librandi, Aug 06 2014
(PARI) Vec(x*(x^11-x^10-x^8-x^7-3*x^6-2*x^5-3*x^4-3*x^3-2*x^2-2*x-1)/((x-1)^3*(x+1)*(x^2-x+1)*(x^2+x+1)^2) + O(x^100)) \\ Colin Barker, Aug 06 2014
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, May 25 2003
STATUS
approved