OFFSET
1,2
COMMENTS
The vertices of these figures need not be in [n] X [n].
LINKS
Matthew Coppenbarger, Problem 11060, The American Mathematical Monthly, Vol. 111, No. 1 (2004), p. 65; Little Boxes Made of Ticky-Tacky, Solution to Problem 11060, ibid., Vol. 112, No. 8 (2005), pp. 753-754.
Index entries for linear recurrences with constant coefficients, signature (4,-5,0,5,-4,1).
FORMULA
F_n = (11n^4-2n^3-5n^2-22n+12)/12 for n even and F_n = (11n^4-2n^3-5n^2-22n+18)/12 for n odd. It can also be represented by the floor of the second expression for all n.
G.f.: -x^2*(x^4+8*x^2+26*x+9) / ((x-1)^5*(x+1)). [Colin Barker, Feb 18 2013]
MAPLE
F:= n -> trunc((11*n^4-2*n^3-5*n^2-22*n+18)/12);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jerrold Grossman, Oct 17 2004
STATUS
approved