OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (1,5,-5).
FORMULA
a(n) = 6*5^((n-1)/2)-2 (n odd), 2*5^(n/2)-2 (n even).
a(1)=4, a(2)=8, a(3)=28, a(n)=a(n-1)+5*a(n-2)-5*a(n-3). - Harvey P. Dale, May 30 2012
G.f.: 4*x*(x+1) / ((x-1)*(5*x^2-1)). - Colin Barker, Apr 26 2015
a(n) = 4*A238366(n-1). - Michel Marcus, Apr 26 2015
MATHEMATICA
pal5s[n_]:=If[OddQ[n], 6 5^((n-1)/2)-2, 2 5^(n/2)-2]; Array[pal5s, 40] (* or *) LinearRecurrence[{1, 5, -5}, {4, 8, 28}, 40] (* Harvey P. Dale, May 30 2012 *)
PROG
(PARI) Vec(4*x*(x+1)/((x-1)*(5*x^2-1)) + O(x^100)) \\ Colin Barker, Apr 26 2015
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Martin Renner, May 02 2006
EXTENSIONS
More terms from Harvey P. Dale, May 30 2012
STATUS
approved