OFFSET
1,1
LINKS
FORMULA
a(n) = 4*5^floor((n-1)/2).
a(n) = 5*a(n-2). G.f.: -4*x*(x+1)/(5*x^2-1). [Colin Barker, Feb 15 2013]
MAPLE
MATHEMATICA
LinearRecurrence[{0, 5}, {4, 4}, 40] (* or *) With[{c=NestList[ 5#&, 4, 20]}, Riffle[ c, c]] (* Harvey P. Dale, Apr 18 2019 *)
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Martin Renner, May 02 2006
EXTENSIONS
More terms from Colin Barker, Feb 15 2013
STATUS
approved