OFFSET
1,2
COMMENTS
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..1000[Terms 1 through 300 were computed by Vincenzo Librandi; Terms 301 through 1000 by G. C. Greubel, May 17 2016]
Index entries for linear recurrences with constant coefficients, signature (0,3)
FORMULA
a(n) = (7+(-1)^n)*3^(1/4*(2*n-5+(-1)^n))/2.
G.f.: x*(1+4*x)/(1-3*x^2).
a(n+3) = a(n+2)*a(n+1)/a(n). - Reinhard Zumkeller, Mar 04 2011
a(n) = 3^floor((n-1)/2)*4^(1-n%2). - M. F. Hasler, Dec 03 2014
E.g.f.: (sqrt(3)*sinh(sqrt(3)*x) + 4*cosh(sqrt(3)*x) - 4)/3. - Ilya Gutkovskiy, May 17 2016
MATHEMATICA
LinearRecurrence[{0, 3}, {1, 4}, 50] (* G. C. Greubel, May 17 2016 *)
PROG
(Magma) [ n le 2 select 3*n-2 else 3*Self(n-2): n in [1..35] ];
(PARI) a(n)=3^(n\2)*(4/3)^!bittest(n, 0) \\ M. F. Hasler, Dec 03 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Klaus Brockhaus, Oct 16 2009
STATUS
approved