OFFSET
0,2
LINKS
Colin Barker, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (1,4,-4).
FORMULA
From Colin Barker, Mar 17 2017: (Start)
G.f.: (1 + x - 2*x^2 - x^3) / ((1 - x)*(1 - 2*x)*(1 + 2*x)).
a(n) = (8 + (-2)^n + 21*2^n) / 24 for n>0.
(End)
MATHEMATICA
LinearRecurrence[{1, 4, -4}, {1, 2, 4, 7}, 50] (* Harvey P. Dale, Jan 14 2019 *)
PROG
(PARI) Vec((1 + x - 2*x^2 - x^3) / ((1 - x)*(1 - 2*x)*(1 + 2*x)) + O(x^50)) \\ Colin Barker, Mar 17 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paul Curtz, Mar 28 2008
STATUS
approved