OFFSET
0,2
REFERENCES
Problem asked by Barry Cipra arising from Problem 89 of Vaderlind, Guy & Larson, The Inquisitive Problem Solver, MAA.
LINKS
Michael De Vlieger, Table of n, a(n) for n = 0..10000
Ruediger Jehn, Properties of Hamiltonian Circuits in Rectangular Grids, arXiv:2103.15778 [math.GM], 2021.
Index entries for linear recurrences with constant coefficients, signature (2,0,-2,1).
FORMULA
a(n) = 4n^2 - 2n if n is even and 4n^2 - 2n - 2 if n is odd and > 1.
From Colin Barker, Oct 05 2012: (Start)
a(n) = -1+(-1)^n-2*n+4*n^2 for n>1.
a(n) = 2*a(n-1)-2*a(n-3)+a(n-4) for n>5.
G.f.: -(4*x^5-7*x^4-6*x^3-4*x^2-2*x-1)/((1-x)^3*(1+x)). (End)
MATHEMATICA
CoefficientList[Series[-(4 x^5 - 7 x^4 - 6 x^3 - 4 x^2 - 2 x - 1)/((1 - x)^3*(1 + x)), {x, 0, 46}], x] (* Michael De Vlieger, Mar 11 2021 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
R. K. Guy, Jul 11 2003
EXTENSIONS
More terms from David Wasserman, May 30 2004
STATUS
approved