OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (1, 2, -2).
FORMULA
a(n) = 2*a(n-2)+11 for n > 2; a(1) = 5, a(2) = 11.
a(n) = (27-5*(-1)^n)*2^(1/4*(2*n-1+(-1)^n))/2-11.
G.f.: x*(5+6*x)/(1-x-2*x^2+2*x^3).
PROG
(Magma) T:=[ n le 2 select n+4 else 2*Self(n-2): n in [1..38] ]; [ n eq 1 select T[1] else Self(n-1)+T[n]: n in [1..#T]];
CROSSREFS
KEYWORD
nonn
AUTHOR
Klaus Brockhaus, Aug 10 2009
STATUS
approved