OFFSET
0,3
LINKS
FORMULA
a(n) = 3(n+3)2^(n-4), n>2.
MATHEMATICA
CoefficientList[Series[(1-3x+4x^2-3x^3+x^4)/(1-2x)^2, {x, 0, 40}], x] (* or *) LinearRecurrence[{4, -4}, {1, 1, 4, 9, 21}, 40] (* Harvey P. Dale, Nov 25 2020 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Jun 12 2003
STATUS
approved