OFFSET
0,2
LINKS
Peter Kagey, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (4,-4).
FORMULA
G.f.: (1 - x^2)/(1 - 2*x)^2.
a(n) = A207615(n+2, 2).
a(n) = 2^(n-2)*(3*n + 5) for n >= 1. - Kevin Ryde, Nov 28 2020
E.g.f.: (exp(2*x)*(5 + 6*x) - 1)/4. - Stefano Spezia, May 14 2023
MAPLE
a := proc(n) option remember; if n <= 2 then return [1, 4, 11][n+1] fi;
4*a(n - 1) - 4*a(n - 2) end: seq(a(n), n = 0..31);
MATHEMATICA
CoefficientList[Series[(1 - x^2)/(1 - 2*x)^2, {x, 0, 50}], x]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Peter Kagey and Peter Luschny, Nov 28 2020
STATUS
approved