OFFSET
0,3
LINKS
Index entries for linear recurrences with constant coefficients, signature (2,3,4,-4).
FORMULA
a(n)=2a(n-1)+3a(n-2)+4a(n-3)-4a(n-4); a(n)=sum{k=0..floor(n/2), C(2(n-k), 2k)2^k}.
a(n) ~ (1+sqrt((4*sqrt(2)-1)/31)) * (1+2*sqrt(2)+sqrt(1+4*sqrt(2)))^n/2^(n+2). - Vaclav Kotesovec, Jul 24 2013
MATHEMATICA
CoefficientList[Series[(1-x-2*x^2)/(1-2*x-3*x^2-4*x^3+4*x^4), {x, 0, 20}], x] (* Vaclav Kotesovec, Jul 24 2013 *)
LinearRecurrence[{2, 3, 4, -4}, {1, 1, 3, 13}, 30] (* Harvey P. Dale, Aug 29 2023 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Jun 04 2005
STATUS
approved